A sensor unit with a sensing surface molded properly on an outer surface of a sensor receiving part is provided. The sensor unit includes a resin casing formed with an annular fixing member, and a sensor receiving part formed in the casing for receiving a sensor housed. A sensing surface that faces a target object is formed within the sensor receiving part. A resin charging position in molding the casing is set to a position deviated circumferentially from a central position in a width of the sensing surface. In particular, resin is charged into the fixing member from a gate arranged on an extending line of a first through-bore formed in a position corresponding to the charging position.