To provide a rechargeable slave unit device in a nurse call system which can be wirelessly connected, reduce a time and a trouble for recharging, and is more economical than that using batteries.

The slave unit device has a handset holder and a handset. The handset holder is composed of contact electrodes, a hook to hang the handset, an electric power supply, and a switch that is turned on when the weight of the handset is applied to the hook to apply a voltage from the power supply to the electrodes. The handset has a hanger provided with contact electrodes which are hung on the hook, and a rechargeable battery which is connected to the contact electrodes of the hanger. When the handset is hung on the holder, the contact electrodes of the hook are contacted with the contact electrodes of the hanger to recharge the handset.