A riding-type mower comprising: a vehicle body; and a mower unit which is connected to a front side of the vehicle body, wherein the mower unit has a rotatable cutting blade (21, 22, 23) which cuts grass or lawn while rotating, and a mower deck which accommodates the rotatable cutting blade (21, 22, 23) and is provided with a cut grass discharge opening in a rear portion of the mower deck; the mower deck is provided with a cut grass guide member which inclines downward and to a rear side of the cut grass discharge opening; and each of a width of the mower deck and a width of the cut grass guide member is wider than a width of the vehicle body with respect to a right-left direction of the vehicle body, characterized in that the mower deck is constructed so that posture of the mower deck can be changed into any one of a first posture, in which it is possible to cut the grass or lawn, and a second posture in which an inside of the mower deck faces toward a forward direction of the vehicle body, a guard member is disposed on an upper surface of the cut grass guide member behind each part of the discharge opening being outside of the vehicle body with respect to the right-left direction of the vehicle body, the guard member is constructed in such a manner that the guard member can be turned about an axis, the guard member has a rear part which is disposed in a predetermined distance from the cut grass discharge opening and located near the ground, and side parts (152a, 152c) disposed so as to incline along the cut grass guide member and extend backward at the time when the mower deck is allowed to be in the first posture, and the guard member is rotatable about the axis in order to be disposed at a position where the guard member does not touch the ground at the time when the mower deck is allowed to be in the second posture. a vehicle body; and a mower unit which is connected to a front side of the vehicle body, wherein the mower unit has a rotatable cutting blade (21, 22, 23) which cuts grass or lawn while rotating, and a mower deck which accommodates the rotatable cutting blade (21, 22, 23) and is provided with a cut grass discharge opening in a rear portion of the mower deck; the mower deck is provided with a cut grass guide member which inclines downward and to a rear side of the cut grass discharge opening; and each of a width of the mower deck and a width of the cut grass guide member is wider than a width of the vehicle body with respect to a right-left direction of the vehicle body, characterized in that the mower deck is constructed so that posture of the mower deck can be changed into any one of a first posture, in which it is possible to cut the grass or lawn, and a second posture in which an inside of the mower deck faces toward a forward direction of the vehicle body, a guard member is disposed on an upper surface of the cut grass guide member behind each part of the discharge opening being outside of the vehicle body with respect to the right-left direction of the vehicle body, the guard member is constructed in such a manner that the guard member can be turned about an axis, the guard member has a rear part which is disposed in a predetermined distance from the cut grass discharge opening and located near the ground, and side parts (152a, 152c) disposed so as to incline along the cut grass guide member and extend backward at the time when the mower deck is allowed to be in the first posture, and the guard member is rotatable about the axis in order to be disposed at a position where the guard member does not touch the ground at the time when the mower deck is allowed to be in the second posture.