PROBLEM TO BE SOLVED: To provide a biological signal detection device that can output a signal with a large S/N ratio.SOLUTION: A biological signal detection device 100 includes: a reference pulse generation part 1; a photo-reflector 2; a reference voltage control part 5; a DUTY variation rate detection part 3; and a biological signal generation part 6.SELECTED DRAWING: Figure 1【課題】S/N比の大きな信号を出力することのできる生体信号検出装置を提供する。【解決手段】生体信号検出装置100は、リファレンスパルス発生部1、フォトリフレクタ2、基準電圧制御部5、DUTY変化量検出部3、生体信号生成部6を含む。【選択図】図1