1. A breast tomography apparatus comprising: a gantry incorporating a radiation source and a radiation detector; a breast insert portion which is provided in said gantry and in which a breast as an imaging target is to be inserted; a detection unit which is arranged on said gantry and includes a contact detection sensor configured to detect contact with an object; and a determination unit configured to determine an insert condition of the breast into said breast insert portion based on detection of contact by said contact detection sensor.