In a combustion pressure sensor, a sensor holder is installed in a housing. The sensor holder has an end contact surface. A load transfer member is installed in the housing. The load transfer member has a contact surface facing the end contact surface of the sensor holder. The contact surface of the load transfer member is in contact with the end contact surface of the sensor holder. One of the contact surface of the load transfer member and the end contact surface of the sensor holder has a concavely curved shape, and the other thereof has a convexly curved shape.