A work machine provided with an exhaust gas purifying device includes a selective catalytic reducing device that performs treatment on exhaust gas of an engine, and a reducing agent injection device that injects a reducing agent into exhaust gas to be supplied to the selective catalytic reducing device. The work machine is provided with a housing that delimits an engine room accommodating the engine and the exhaust gas purifying device. The housing includes a top board that covers the engine room above the engine, and an exhaust duct that is provided in the top board and discharges the air in the engine room to the outside of the engine room. A part of a reducing agent supply pipe for guiding the reducing agent to the reducing agent injection device is disposed in the exhaust duct in a position above the reducing agent injection device.