Waterproof case assembly structure

A waterproof case assembly structure in which bosses each provided for a different one of first and second cases being separate are fixed by a screw, while an annular sealing body is sandwiched at a part where the respective bosses of the first and second cases abut against each other, the waterproof case assembly structure comprising:

• an annular groove;
• which is provided so as to surround the screw on an abutting face of the boss of the first case, and
• with which the sealing body is arranged;
• a plurality of branch grooves:
• being contiguous with the annular groove, and
• extending outside an annular shape thereof;
• tongue pieces provided so as to:
• extend outside an annular shape of the sealing body, and
• be inserted into the branch grooves;
• a pressing member:
• being attached, as a separate element, to the first case, and
• pressing the tongue pieces inside the branch grooves;
• and
• a position determining part that determines a position of the pressing member to be such a position that the tongue pieces are pressed inside the branch grooves.