A pipe supporting device includes a support portion for supporting a hydraulic pipe along an axis of the hydraulic pipe extending along a length of a boom, and a weld portion to be connected with an outer surface of the boom by fillet welding. The weld portion has a plurality of peripheral surfaces, the plurality of peripheral surfaces including: a pair of opposite perpendicular standing surfaces and extending in a direction substantially perpendicularly intersecting a first stress direction along the axis of the hydraulic pipe; and a pair of oblique standing surfaces extending from respective leading ends of the pair of opposite perpendicular standing surfaces to join each other. Each of the oblique standing surfaces extends in a direction oblique to the first stress direction and joins the corresponding one of the perpendicular standing surfaces at an acute angle.
