The present invention is intended to provide constant drive conditions of a relay switch. A relay drive circuit includes a current mirror circuit, a current suppression circuit 26, and a transistor Q3. The current mirror circuit includes a transistor Q1, a first resistor element R1, a transistor Q2, and a second resistor element R2. A relay coil 18 is provided on a current supply path extending from a collector terminal of the transistor Q1 to an earth conductor. The current suppression circuit 26 includes a capacitor C1 as a current suppression element configured to suppress, after conduction between an emitter terminal and a collector terminal of the transistor Q2 has been made, the current flowing through the current suppression element itself as compared to that in such conduction.