A walk-behind lawnmower having a height adjusting mechanism for adjusting the height of a housing above the ground. The height adjusting mechanism includes: a front wheel supporting member and a rear wheel supporting member that are attached to the housing so as to be capable of swinging up and down a linking member for linking the front and rear wheel supporting members so as to be capable of concerted motion and a locking mechanism for restricting and releasing displacement of the linking member in the forward-and-backward direction. The locking mechanism includes: a plurality of locking grooves arranged in a row from front to rear on the linking member a locking pin capable of selectively interlocking with one of the locking grooves a pin-guiding part for guiding the locking pin to be capable of entering into and retracting from one of the locking grooves and an operating member for sliding and operating the locking pin.
