To make a foreign matter attracted by a magnet not to be released to a circulation path of lubricating oil even if it is separated from the magnet, while improving the efficiency of the recovery of the foreign matter, in the structure that attracts and collects the foreign matter by using the magnet.

The structure includes: a shift rod chamber 715 where a shift rod 27 that operates a reversing mechanism is accommodated; a guide part 701 in which a guide surface 702 that is formed at a lower end of the shift rod chamber 715 and inclines with a prescribed angle to the axis line of the shift rod; a lubricating oil trap 703 that is formed like the cup that has an opening at the upper side and closes the lower side, and the opening is formed in the guide surface; and a magnet 704 that is accommodated internally of the lubricating oil trap 703, and attracts the foreign matter included in the lubricating oil.