To prevent grease leaking out from a bearing part supporting the proximal end side of a boom and/or a boom cylinder from being deposited in a narrow gap in a lower portion of the bearing part.

A work machine includes a turning frame 3, a boom 15 attached to the turning frame so as to be movable upward and downward through the bearing part and a connection pin 21, and a boom cylinder 18 attached to the turning frame so as to be freely turned through the bearing part and a connection pin 22 and also move the boom up and down. To at least one of the connection part of the boom to the turning frame and the connection of the boom cylinder to the turning frame, one end of elastic plate materials 25 and 26 is attached. Also, the other end of the plate materials is moved back and forth in linkage with the turning operation of the boom or the boom cylinder on the turning frame in the lower part of the connection pin. Thus, the grease dropped from the connection pin part onto the turning frame is extruded by the plate materials.