The annual life cycle of adult Z. zebra, a heterosomata fish in Seto Inland Sea, mainly focused on maturity and spawning was examined by 296 samples caught in the nearshore waters around Imabari from July 1999 to November 2001. Body lengths of samples were 101-236mm in males (128 fish) and 102-301mm in females (168 fish), which data suggested female has a tendency to grow bigger than male. The biological minimum size, 125mm of male and 175mm of female, also indicated the inclination. Judging from the gonadsomatic index (GSI), hepatosomatic index (HSI), and condition factor (CF) of adult fish, the annual life cycle of this species was calculated as follows: spawning season is from June to August, pre-spawning season and recovering season from spawning are from May to June and from August to September, respectively, pre-wintering season is from October to December and wintering season is from January to March. One modes in frequency distributions of egg diameter was found from the ovaries of samples during spawning season. It was estimated that the spawning of this species is performed by spawning their eggs some times after the mass of eggs indicated by one mode in frequency distribution of egg diameter becomes a mass of large-sized egg more than 0.7mm in egg diameter and the rate of the mass in the ovary reaches around 90%. The fecundity of this species was from thirty thousand to fifteen hundred thousand per individual, and there was a plus correlation of body length (BL) with fecundity (F) : F = 3.23 × 10-5 BL3.94, r; 0.884.