To provide a game machine island capable of suppressing fraudulence performed by inserting an upper arm from an inspection port and suppressing disadvantages on a game hall side.

A transom 10 includes: a plate member 11 formed in such a shape that it is possible to cover the inspection port 3; a turning support member 12 installed at the lower part of the plate member 11 for supporting the plate member 11 turnably between a position to close the inspection port 3 and a position to open it; and an open position limiting member 13 for limiting the turning of the plate member 11 below a position (roughly horizontal position, hereafter) at which the plate member 11 is positioned roughly horizontal. The dimension of the plate member 11 is determined so that the amount of the plate member 11 projecting from the inspection port 3 in the horizontal direction when positioned at the roughly horizontal position is equal to or more than an amount determined on the basis of the length of the upper arm of a human being. Thus, in the case that the plate member 11 is at the roughly horizontal position, even if the human being tries to insert the upper arm from the lower part of the inspection port 3, the plate member 11 becomes obstructive and the upper arm does not easily reach the inspection port 3.