A circuit unit (10) includes a circuit body (11) having a resin portion (12) covering a circuit, first terminals (15) projecting from one edge of the resin portion (12) and second terminals (16) projecting from another edge part of the resin portion (12). A fixing member (20) made of metal is configured to fix the circuit body (11) to a base member (BM) by being mounted on the base member (BM) while being held in contact with the resin portion (12). A cover (30) having receptacles (35, 36) is fit to mating connectors (50A, 50B) while covering the first and second terminals (15, 16). The cover (30) is configured to cover the circuit body (11) and the fixing member (20). The cover (30) is formed with an opening (33) for exposing the fixing member (20) to outside.