The gonadosomatic index (GSI), sex steroid hormones and gonadal development of roughscale sole Clidoderma asperrimum cultured in indoor tank were investigated to evaluate its sexual maturation and reproductive cycle. The highest GSI values of female and male were $6.91{pm}4.03$ (May) and $0.16{pm}0.08$ (August), respectively. The reproductive cycle would be classified into four successive developmental stages: growing stage (December to February), maturation stage (March to April), ripe and spawning stage (May to June), recovery and resting stage (July to November). The highest plasma testosterone (T) and estradiol-$17{eta}$ ($E_2$) levels of female were $259.4{pm}76.8$ and $633.3{pm}182.5$ pg/mL, respectively in May. Also $17{alpha}$, $20{eta}$-dihydroxy-4-pregen-3-one ($17{alpha}$, $20{eta}$-OHP) levels of female peaked in April before spawning season ($244.2{pm}42.5$ pg/mL). The highest plasma testosterone (T) and 11-ketotestosterone levels of male were $231.0{pm}46.0$ and $273.9{pm}54.5$ pg/mL, respectively in April. But there was no significant difference in $17{alpha}$, $20{eta}$-OHP.