A biosignal sensing device (2) includes an electrode section (12) including a pair of electrodes (12a,12b) mounted so that a living body can be in close proximity to or in contact with the electrodes. An oscillation section (11) supplies a high frequency signal to the electrodes. A reflected-wave level from the electrodes receiving the high frequency signal changes according to a change in impedance in the electrodes that are in close proximity to or in contact with the living body. This change in reflected-wave level reflects a change in impedance resulting from body movement of the living body such as respiration and pulsation. A sensing section (13) senses a signal indicating the change in reflected-wave level. Based on this signal, a signal amplifying section (14) calculates a desired biosignal such as pulse rate and respiration rate.