Ocellated octopus (Octpus ocellatus) is one of economically important octopus species in Japan. Here, we showed spawning characteristics and embryonic development, which were essential for the management of natural resource and the establishment of aquaculture techniques for this species. During the period from March to June, 2015, each pair of ocellated octopus was maintained in 10L-tank. Female parents started to lay eggs on the wall of tanks from 9 to 26 days after starting of rearing. During this spawning period from 2nd April to 22nd May, 2015 (at the water temperature of 13.1 to 19.7 ℃), average 17.2 spawning events with average 16.6 eggs from single octopus female were observed. Embryo reached the organogenesis-stage at 17 days post spawning (dps), and then newly hatchlings occurred at average 59.3 dps.