A portable radiographic imaging device including: a radiation detection panel including optoelectric conversion elements that convert irradiated radiation into an electrical signal; a signal processing substrate performing predetermined signal processing on the input electrical signal; a holding base provided between the radiation detection panel and the signal processing substrate and holding the signal processing substrate; a flexible substrate including a flexed portion, with one end of the flexible substrate being connected to the radiation detection panel and the other end of the flexible substrate being connected to the signal processing substrate; a casing in which the radiation detection panel, the signal processing substrate, the holding base and the flexible substrate are installed; and a contact avoidance portion formed at at least one of the signal processing substrate, the holding base or the casing such that contact of with the flexible substrate is avoided, is provided.