A temperature detector for measuring temperature of a heat exchanger of a vehicular air-conditioning unit includes a holder holding temperature measuring means for measuring the temperature of the exchanger and a harness connected to the measuring means. The holder has a through hole through which a measuring section of the measuring means extends, and first and second grip parts through which the harness extends. The first grip part has such a width dimension that the harness having a width dimension in the horizontal direction can be inserted therethrough, and the second grip part has such a width dimension that the harness having the width dimension in the vertical direction can be inserted therethrough and that the harness having the width dimension in the horizontal direction can not be inserted therethrough. Accordingly, a portion of the harness between the first and second grip parts is twisted and held by the holder.