In a display screen support mechanism, a first hole portion receiving a platelike support shaft is provided in the form of a symmetrical sector formed by connecting two sectoral forward ends which are symmetric with respect to a hole center, and a display screen support member is rotatable about the platelike support shaft serving as a rotating shaft within an angular range of the symmetrical sectoral hole portion in a state where an end of the platelike support shaft in a longitudinal direction comes into contact with an arcuate inner peripheral surface of the symmetrical sectoral hole portion.