A typical interplate earthquake with M7.2 occurred on August 16, 2005 on the plate boundary off Miyagi Prefecture. Co- and post-seismic deformations associated with this event were investigated to reveal the causal interplate slips using continuous GPS data and geodetic inversion. The co-seismic slip distribution shows good agreement with that estimated by seismic waveform inversions. The major slip area is limited to the southeastern part of the rupture area of the 1978 Miyagi-oki earthquake (M7.4). The post-seismic slip extended uni-laterally to the southwest of the co-seismic slippage. These distinctive features both of the co- and post-seismic slips might be caused by the existence of the locked plate interface in the northern and southwestern parts of the 1978 rupture area, where seismogenic stress has not released yet.