A walk-behind self-propelled machine, comprising: a drive motor (30); a handle (41), provided with two grip portions (411a, 411b) for allowing a user to grip by the left and right hands; a speed adjusting member (42), moving relative to the handle (41) so as to adjust the rotational speed of the drive motor (30), the speed adjusting member (42) being able to be operated by a user when the user grips either of the grip portions by one hand, and the speed adjusting member (42) being provided between the two grip portions (411a, 411b); and an electromechanical conversion device (43), producing, on the basis of the position change of the speed adjusting member (42) relative to the handle (41), an electrical signal for adjusting the rotational speed of the drive motor (30); the speed adjusting member (42) moves, relative to the handle (41), between a first position and a second position; the rotational speed of the drive motor (30) at the time when the speed adjusting member (42) is located at the first position i
