A detector includes a stylus, a holding portion that holds a proximal end portion of the stylus, a body portion that supports the holding portion rotatably about a rotational axis, and a sensor that detects a rotational displacement of the holding portion. The holding portion includes an abutting member, on which the proximal end portion of the stylus abuts, and a plate spring that biases the proximal end portion of the stylus against the abutting member. The abutting member includes a groove portion on which the proximal end portion of the stylus abuts, and a semispherical portion that extends toward the plate spring, compared with a bottom of the groove portion. The stylus includes a proximal end inclined portion at the proximal end portion of the stylus. The proximal end inclined portion is inclined toward the plate spring, with a decreasing distance from the rotational axis.