Seven ergosterol derivatives (1-7) were isolated from silkworm larvae infected with Paecilomyces sp. J300. On the basis of spectroscopic means, their structures have been elucidated as 3$eta$,5$alpha$-dihydroxy-ergosta-7,22-diene (1), 5$alpha$,6$alpha$-epoxy-(22E,24R)-ergosta-8(14), 22-diene-3$eta$,7$alpha$-diol (2), 5$alpha$,6$alpha$-epoxy-(22E,24R)-ergosta-8, 22-diene-3$eta$,7$alpha$-diol (3), ergosta-4, 6, 8(14), 22-tetraene-3-one (4), ergosterol (5), ergosterol endoperoxide (6), 3$eta$,5$alpha$-dihydroxy-6$eta$-methoxyergosta-7,22-diene (7). Compounds 3~7 showed moderate cytotoxicity against five tumor cells.