A coin outlet unit is disclosed to include a casing having a coin outlet, and an adjustment structure for adjusting the size of the coin outlet. The adjustment structure positioning spaces arranged in a line perpendicular to the extending direction of the coin outlet, locating holes arranged in parallel to the positioning spaces, an adjustment block, which has a bottom rod selectably inserted into one of the positioning spaces and a plurality of adjustment holes, and a locking member insertable through the adjustment holes into the locating holes to lock the adjustment block.