A projector and a supporting structure thereof are provided. The projector includes a main body and a supporting structure. The supporting structure is disposed at the main body. The supporting structure includes a sliding element and an elastic element. The sliding element is supported on a plane and can move backward and forward with respect to the main body. The elastic element has a first end and a second end. The first end is coupled to the sliding element, and the second end is coupled to the main body. The elastic element generates a substantially constant elastic force when the elastic element is deformed. As the sliding element moves with respect to the main body, the elastic force balances against the gravity force of the main body, such that the elevational angle of the main body with respect to the plane is changed.