A wheel loader comprising: a driver's cab; an engine; a chassis, at sides of which tires are provided; an engine room (11, 61) in which the engine is mounted on the chassis, the engine room (11, 61) being provided behind the driver's cab and including an upper cover (16, 66) covering an upper portion of the engine room (11, 61), wherein the upper cover (16, 66) includes a muffler (41, 91) configured to discharge an exhaust gas; and a frame structure (15,65) including front portion structures (12, 62) respectively standing at left and right positions of a surface of the engine room (11,61), the surface being located at a driver's cab side and rear portion structures (13, 63) respectively standing at left and right positions of a surface of the engine room (11,61), the surface being opposite to the surface located at the driver's cab side; characterized in that: the frame structure (15, 65) comprises a coupling structure (14, 64) that is provided in the engine room (11, 61) and above the engine, the coupling structure coupling upper portions of the front portion structures to upper portions of the rear portion structures and forms a peripheral device installation space (30, 80) above the engine and between the coupling structure (14, 64) and the upper cover (16, 66), a peripheral device being provided on the coupling structure (14, 64); the coupling structure (14, 64) including a dividing plate (32, 82) dividing the peripheral device installation space (30, 80) into an exhaust system peripheral device installation space (31,81) and an intake system peripheral device installation space (33, 83); and the muffler (41, 91) including an opening portion (45, 95) through which air in the exhaust system peripheral device installation space (31, 81) is discharged to an outside by an upward flow generated by the exhaust gas discharged from the muffler (41, 91). a driver's cab; an engine; a chassis, at sides of which tires are provided; an engine room (11, 61) in which the engine is mounted on the chassis, the engine room (11, 61) being provided behind the driver's cab and including an upper cover (16, 66) covering an upper portion of the engine room (11, 61), wherein the upper cover (16, 66) includes a muffler (41, 91) configured to discharge an exhaust gas; and a frame structure (15,65) including front portion structures (12, 62) respectively standing at left and right positions of a surface of the engine room (11,61), the surface being located at a driver's cab side and rear portion structures (13, 63) respectively standing at left and right positions of a surface of the engine room (11,61), the surface being opposite to the surface located at the driver's cab side; front portion structures (12, 62) respectively standing at left and right positions of a surface of the engine room (11,61), the surface being located at a driver's cab side and rear portion structures (13, 63) respectively standing at left and right positions of a surface of the engine room (11,61), the surface being opposite to the surface located at the driver's cab side; characterized in that: the frame structure (15, 65) comprises a coupling structure (14, 64) that is provided in the engine room (11, 61) and above the engine, the coupling structure coupling upper portions of the front portion structures to upper portions of the rear portion structures and forms a peripheral device installation space (30, 80) above the engine and between the coupling structure (14, 64) and the upper cover (16, 66), a peripheral device being provided on the coupling structure (14, 64); the coupling structure (14, 64) including a dividing plate (32, 82) dividing the peripheral device installation space (30, 80) into an exhaust system peripheral device installation space (31,81) and an intake system peripheral device installation space (33, 83); and the muffler (41, 91) including an opening portion (45, 95) through which air in the exhaust system peripheral device installation space (31, 81) is discharged to an outside by an upward flow generated by the exhaust gas discharged from the muffler (41, 91). the frame structure (15, 65) comprises a coupling structure (14, 64) that is provided in the engine room (11, 61) and above the engine, the coupling structure coupling upper portions of the front portion structures to upper portions of the rear portion structures and forms a peripheral device installation space (30, 80) above the engine and between the coupling structure (14, 64) and the upper cover (16, 66), a peripheral device being provided on the coupling structure (14, 64); the coupling structure (14, 64) including a dividing plate (32, 82) dividing the peripheral device installation space (30, 80) into an exhaust system peripheral device installation space (31,81) and an intake system peripheral device installation space (33, 83); and the muffler (41, 91) including an opening portion (45, 95) through which air in the exhaust system peripheral device installation space (31, 81) is discharged to an outside by an upward flow generated by the exhaust gas discharged from the muffler (41, 91).