To easily obtain a flat hinge with a catch mechanism.

A socket 20 at a side of a door 3 and a hinge body 40 at a side of a housed article body 2 are connected by two inner and outer arms 51 and 52, a cam member 61 is disposed in a freely forward and backward movable manner so as to be linearly displaced within the inner arm 51 while being energized by a spring 62, and a cam surface 61C of the cam member 61 is engaged with a cam engage roller 63R which is mounted within the hinge body 40, at a socket intermediate (open) position, to hold the socket intermediate position.