A fixing device includes a fixing member, a pressuring member, a fixing device main body, a guide member and a detecting mechanism. The guide member is rotatable between a closing position where the guide member covers a sheet conveying path and an opening position where the guide member exposes the sheet conveying path. The detecting mechanism includes a sensor and an actuator. The sensor includes a light emitting part and a light receiving part. The actuator is swingable between a non-blocking position where the actuator does not block a light and a blocking position where the actuator blocks the light. When the actuator rotates integrally with the guide member according to a rotation of the guide member between the closing position and the opening position, the actuator passes between the light emitting part and the light receiving part.