A supporting mechanism for movably supporting a member to be supported along a supporting shaft, comprises supporting members and a pressing device. The supporting members are provided on the member to be supported. Each of the supporting members comes into contact with the supporting shaft on at least two contact points so as to be movable on the supporting shaft. The at least two contact points are apart from each other. The pressing device presses the supporting members against the supporting shaft so that the contact points of each supporting member simultaneously come into contact with the supporting shaft.