A heartbeat detection device includes a pair of electrode units, a transmitting unit and a receiving unit. The transmitting unit is electrically connected to the paired electrode units each by respective wires. The paired electrode units each include an electrode body and a hook sandwiching a bottom part of a garment for example on a body for holding the electrode units on respective predetermined parts of the body. The hook is formed on the front side of the electrode unit. The transmitting unit includes a transmitting-unit body and a hook sandwiching an upper part of the garment for holding the transmitting unit on the garment. The hook is formed on the rear side of the transmitting unit. The lightweight heartbeat detection device is thus achieved that can ensure electrical contact between the electrode units and respective predetermined parts of the chest without causing a feeling of tightness.