In this study we conducted a survey of supporters involved with assisting children’s development to assess competency in five areas created to organize the necessary abilities and qualities of supporters engaged in assisting children with disabilities in order to explore the areas of expertise of supporters involved with assisting children with disabilities in infancy, and we examined competency models. The survey had a total of 145 questions comprised of 24 interest, will and attitude questions, 27 knowledge questions, 36 skill questions, 22 practice and reflection questions, and 33 foundational strength of members of society questions. The respondents to the survey who were employees of child development support centers and child development support businesses in region A (8 prefectures) were asked to anonymously complete the questionnaire. We targeted 611 people (38 managers including facilities managers, and assistant facilities managers etc., 42 child development support managers, 500 employees, 32 non-respondents). The Cronbach α coefficient was determined for each area of the competency assessment created, and a high value exceeding 0.9 was obtained in each area, confirming a high reliability in competency assessment of all areas. In addition, as a result of performing the principal component analysis for each area, the principal component loading amount of the first component in each of the five areas exceeds 0.3, concluding that the first principal component score could be used as a total evaluation reflecting each area (competency acquisition level). Covariance analysis adjusted for age and gender was used to examine the relationship between job title and years of experience and the competency degree of each field (first principal component score). As a result, a significant linear relationship was found between the high-low job position and the degree of competency in the two areas of "knowledge" and "skill", and those with higher positions had higher competencies. Also, a significant linear relationship was found between the number of years of experience and the degree of competency in the four areas of “interest, will and attitude", "knowledge", "skill", and "practice and reflection", and those with more years of experience had higher competencies. Based on these results, as a competency model of supporters engaged in assisting children with disabilities in infancy, we created two models, one for supporters in the initial stages of their careers with less than 3 years of experience and one for career supporters with over 3 years of experience. Because the acquisition of competency is deeply related to the years of experience and job position, we believe that the competency model can be effectively utilized as a tool to support the professional career formation process.