A setting unit selects and sets one of a plurality of commercial power frequencies. A frame rate setting unit sets a frame rate corresponding to the commercial power frequency set by the setting unit. A control unit controls an imaging unit such that imaging is carried out at the frame rate set by the frame rate setting unit to thereby acquire image data successively. A detection unit detects a scanning line part at which luminance changes to differ between image data items successively acquired by the control unit. A changing unit changes the commercial power frequency set by the setting unit in accordance with a detection result obtained by the detection unit.