A fetal state estimation apparatus estimates a state of a fetus in a maternal body based on a potential signal indicating a change in potential on a surface of the maternal body. The fetal state estimation apparatus is configured to include a rotation angle estimation unit which estimates a rotation angle of the fetus with respect to the maternal body at every beating of a heart of the fetus based on the potential signal and a fetal movement estimation unit which estimates a fetal movement which is a movement of the fetus based on the potential signal and the estimated rotation angle.