Fine structrue of the band at 363.52 nm in multiphoton ionization spectrum of SiH4 has. been observed using dye laser with 6×10-4nm scanning step. In the case of three-photon resonant excitation, SiH4 is treated as a a symmetric top. Most rotational lines have been resolved and acounted for as a Q-branch of v2 perpendicular band, and B＇= 3.04±0.01 cm-1 is thus obtained.