A resin substrate includes a resin base material including a first main surface, electrode pads provided on the first main surface, circuit conductor patterns, a resist film, and a coverlay film. The resist film includes, on the outer circumference, a plurality of protruding portions each of which has a tapered shape with a vertex. A portion of the circuit conductor patterns are covered with the resist film, and the coverlay film covers a portion of the resist film including the protruding portions and exposed portions of the circuit conductor patterns. The protruding portions are located at positions sandwiching the exposed portions of the circuit conductor patterns.