Morphology of antennal sensilla and their distribution were investigated in male and female adults of Gymnosoma rotundatum, a parasitic fly to hemipteran species, using scanning electron microscopy. The overall length of antenna was not different between male and female. Antenna of G. rotundatum was composed of scape, pedicel and funiculus in both sexes. Three types of sensilla (sensillum basiconica, s. chaetica and s. coeloconica) were identified from both sexes, in varying numbers and distribution along the antennae. The two sensillum types were further divided into different subtypes; s. basiconica into three subtypes and s. chaetica into two subtypes. Among sensilla, s. basiconica subtype 1, 2 and 3 were multiporous, indicating that the ir primary function is olfactory, and others were not. The s. basiconica was most numerous on the antennae in both sexes. The number of subtype 1 of s. basiconica was different between male and female. The morphological information obtained in our study provides a basis for electrophysiological and behavioral studies of the olfactory sensory function of each morphological type of sensilla. (Supported by PJ011756022018, RDA)