To solve various problems of a conventional hinge mechanism which requires a special purpose tool because a stopper part bent in an L-shape is formed at its end as a stopper means of a hinge pin and engaging grooves or engaging holes at another end and a retaining ring or a snap pin mounted on these engaging grooves or engaging holes should be used as separate parts.

In a structure for rotatably supporting a second member 3a with a first member 2, the hinge mechanism 4 is provided wherein engaging holes 5h, 6h are respectively provided in supporting arms 5, 6 and the hinge pins 7 structuring the stopper part 8 by bending its end in the L-shape are inserted to these engaging holes and an engaging part 9 for engaging the stopper part at a position where the hinge pins move in a coming-off direction and an engaging state is maintained is provided for the first member.