A camera body formed with: a grip portion for a user to grasp when photographing, the grip portion having a back face side and a front face side, wherein a direction from the back face side to the front face side is defined as a front direction, a concave portion, connected with the grip portion, on/from which an imaging unit can be attachably and detachably mounted/removed, the imaging unit being provided in a rectangular case with an optical system, an imaging device and a unit side connector portion, and a body side connector portion, in the concave portion, which is connectable to the unit side connector portion, such that the camera body can be integrated with the imaging unit, so that the combination of the imaging unit and the camera body can be used for photographing a subject, wherein the concave portion includes three wall portions (1B, 1C, 1D) comprising a back wall portion, a side wall portion to which the grip portion is connected, and an upper wall portion on which a release button is provided, wherein a back face of the rectangular case of the imaging unit faces the back wall portion, a left side face of the rectangular case faces the side wall portion, and an upper face of the rectangular case faces the upper wall portion, when the imaging unit is mounted on the concave portion when viewed from the subject side in a direction of the optical axis of the optical system, wherein the camera body includes a locking member for locking the imaging unit in cooperation with a locking member to be locked formed in the imaging unit, wherein an unlocking operation member, on the grip portion, for unlocking a lock of the camera body and the imaging unit by means of the locking member which is disposed in an intersection portion of the side wall portion and the upper wall portion, and wherein the concave portion is opened toward three orthogonal directions consisting of a lower direction, the front direction and a right direction that is orthogonal to the lower direction and the front direction when viewed from the subject side in a direction of the optical axis of the optical system. a grip portion for a user to grasp when photographing, the grip portion having a back face side and a front face side, wherein a direction from the back face side to the front face side is defined as a front direction, a concave portion, connected with the grip portion, on/from which an imaging unit can be attachably and detachably mounted/removed, the imaging unit being provided in a rectangular case with an optical system, an imaging device and a unit side connector portion, and a body side connector portion, in the concave portion, which is connectable to the unit side connector portion, such that the camera body can be integrated with the imaging unit, so that the combination of the imaging unit and the camera body can be used for photographing a subject, wherein the concave portion includes three wall portions (1B, 1C, 1D) comprising a back wall portion, a side wall portion to which the grip portion is connected, and an upper wall portion on which a release button is provided, wherein a back face of the rectangular case of the imaging unit faces the back wall portion, a left side face of the rectangular case faces the side wall portion, and an upper face of the rectangular case faces the upper wall portion, when the imaging unit is mounted on the concave portion when viewed from the subject side in a direction of the optical axis of the optical system, wherein the camera body includes a locking member for locking the imaging unit in cooperation with a locking member to be locked formed in the imaging unit, wherein an unlocking operation member, on the grip portion, for unlocking a lock of the camera body and the imaging unit by means of the locking member which is disposed in an intersection portion of the side wall portion and the upper wall portion, and wherein the concave portion is opened toward three orthogonal directions consisting of a lower direction, the front direction and a right direction that is orthogonal to the lower direction and the front direction when viewed from the subject side in a direction of the optical axis of the optical system.