Empirical relations between short-period source spectra and seismic moment for dip-slip and strike-slip crustal earthquakes in Japan, ranging moment magnitude from 5.7 to 6.9, are developed by spectral inversion method using near-fault strong motion records. The short-period source spectrum A for dip-slip earthquakes is 1.45 times of A by Dan et al.'s empirical relation for crustal earthquakes in the world. The A for strike-slip earthquakes is 0.64 times of A by Dan et al.'s relation. The A calculated from previous source models estimated by empirical Green's function method has the similar trend. The combined asperity area of the previous source models has no differences between dip-slip and strike-slip crustal earthquakes and is 0.8 times of Somerville et al.'s relation for crustal earthquakes in the world. On the other hand, the A for interplate earthquakes in eastern Japan, ranging moment magnitude from 6.6 to 8.2, estimated by spectral inversion method in previous studies is found to be 1.63 times of A by Dan et al.'s relation.