To provide a method of sex reversal in globefish by which genetic males are certainly changed to functional females with estrogen.

The method comprises a step in which globefish, which belongs to Tetraodontiformes and the milt of which is edible, are exposed to breeding water to which estrogen is added. Thereby, the genetic males of globefish which have sex chromosomes consisting of XY are changed to functional females which have sex chromosomes consisting of XY but have ovaries. The globefish are preferably exposed to estrogen periodically at the concentration of 0.1-100 wt.ppb, 1-7 times/week, and 0.5-6 h/time during the period when the gonad has sexual plasticity. Estradiol is preferable as estrogen. From the functional females thus obtained, finally only males are producible (all globefish obtained are males).

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