Macrophthalmus microfylacas (Crustacea: Decapoda: Macrophthalmidae) was colledted from a tical flat in Uranouchi Inlet, Tosa Bay, Kochi Prefecture, Japan. A total of 17 crab specimens were obtained from September 2012 to December 2017, of which three were ovigerous. The specimens were identified as M. microfylacas by the characters of small body size, long eye peduncle and the shape of male cheliped.