There is provided an inspection device for inspecting an inner surface of a nozzle provided in a reactor vessel. The inspection device includes: a device frame, an inspection unit provided on the device frame, an inspection unit push-out moving mechanism for pushing out and moving the inspection unit to the inner surface of the nozzle, a rotation moving mechanism for rotating and moving the inspection unit, a calibration test unit arranged on the device frame for calibrating the inspection unit; and a calibration test unit forward/backward moving mechanism for moving the calibration test unit forward or backward in the direction along the central axis with regard to a track where the inspection unit makes push-out movement.