A work machine comprising: a body frame that is supported against a ground surface by a front wheel and a rear wheel; a boarding operation unit that has an operator seat provided on the body frame; and a ROPS (rollover protection structure) that is installed standing upright on the body frame in the boarding operation unit and has a gate shape when viewed in a front-rear direction, wherein the ROPS includes a pair of left and right vertical column portions, and each of the vertical column portions is constituted by a square pipe material having a rectangular cross section, and has a curved portion at which an upper portion of the vertical column portion is bent forward relative to a lower portion thereof, the curved portion being formed at an intermediate position in an up-down direction of the vertical column portion; and reinforcing bodies each of which spans the upper portion on an upper side of the curved portion and the lower portion on a lower side of the curved portion, wherein each of the reinforcing bodies includes a first reinforcing member that is fitted from a lateral side of a corresponding one of the vertical column portions and has a channel-shaped cross section, a second reinforcing member that has an L-shaped cross section having a face parallel to the front-rear direction of the first reinforcing member, and a face parallel to a left-right direction on a front side or a rear side of the first reinforcing member, and a third reinforcing member having a flat plate shape that intersects the face of the second reinforcing member parallel to the left-right direction and covers an opening side of the channel-shaped cross section of the first reinforcing member. a body frame that is supported against a ground surface by a front wheel and a rear wheel; a boarding operation unit that has an operator seat provided on the body frame; and a ROPS (rollover protection structure) that is installed standing upright on the body frame in the boarding operation unit and has a gate shape when viewed in a front-rear direction, wherein the ROPS includes a pair of left and right vertical column portions, and each of the vertical column portions is constituted by a square pipe material having a rectangular cross section, and has a curved portion at which an upper portion of the vertical column portion is bent forward relative to a lower portion thereof, the curved portion being formed at an intermediate position in an up-down direction of the vertical column portion; and reinforcing bodies each of which spans the upper portion on an upper side of the curved portion and the lower portion on a lower side of the curved portion, wherein each of the reinforcing bodies includes a first reinforcing member that is fitted from a lateral side of a corresponding one of the vertical column portions and has a channel-shaped cross section, a second reinforcing member that has an L-shaped cross section having a face parallel to the front-rear direction of the first reinforcing member, and a face parallel to a left-right direction on a front side or a rear side of the first reinforcing member, and a third reinforcing member having a flat plate shape that intersects the face of the second reinforcing member parallel to the left-right direction and covers an opening side of the channel-shaped cross section of the first reinforcing member.