A rotation angle and stroke amount detection device includes a sensor unit, a rotation angle calculation unit, and a stroke amount calculation unit. The sensor unit includes sin and cos sensors which are magnetic sensing elements that detect changes in a magnetic field caused by rotation or linear displacement of a detection target. The sensor unit outputs sin and cos signals based on detection values of the sin and cos sensors. The rotation angle calculation unit calculates a rotation angle of the detection target based on the sin and cos signals output by the sensor unit. The stroke amount calculation unit calculates a stroke amount of the detection target based on the same signals as those used by the rotation angle calculation unit, i.e., the sin and cos signals. Accordingly, the configuration of the sensor unit may be simplified and the physical size of the device may be reduced.