A mode converter includes a substrate including a first main surface and a second main surface, a first ground conductor layer formed on the first main surface, a second ground conductor layer formed on the second main surface, a plane circuit that is formed on the first main surface and propagates a high frequency, a pin that is connected to the plane circuit, is formed inside a through-hole which penetrate from the first main surface to the second main surface, and communicates with the first main face and the second main surface, and an anti-pad that is formed between an end portion of the pin exposed in the second main surface and the second ground conductor layer.