A radiation imaging apparatus comprises a radiation sensor configured to convert incident radiation to an electrical signal and a housing configured to encompass the radiation sensor, wherein a holding portion that is shaped as a recess is formed in a back face of the housing, the back face being on a side opposite to a radiation incident surface of the housing, and a member having a lower heat conductivity than a heat conductivity of the back face is arranged at a position corresponding to the holding portion in the back face.
