A power unit for driving an electric tool head to which a piston for operating a tool is attached, by pressure-transporting hydraulic oil, the power unit comprising: a first power unit; and a second power unit, wherein the first power unit includes: a first hydraulic pump for pressure-transporting the hydraulic oil; a first motor for driving the first hydraulic pump; and a first fluid passage (e) for pressure-transporting the hydraulic oil from the first hydraulic pump to the electric tool head, and wherein the second power unit includes: a second hydraulic pump for pressure-transporting the hydraulic oil; a second motor for driving the second hydraulic pump; and a second fluid passage (f) for pressure-transporting the hydraulic oil from the second hydraulic pump to the electric tool head; the power unit further comprising: a converging joint for converging the first fluid passage (e) and the second fluid passage (f); a pressure restricting device arranged between the converging joint and the first hydraulic pump to restrict rise in pressure in the first fluid passage (e); and a returning device arranged between the converging joint and the second hydraulic pump to drain the hydraulic oil from the second fluid passage (f) and thereby enable return operation of the piston, wherein the power unit pressure-transports the hydraulic oil from the converging joint to the electric tool head to drive the electric tool head; characterised in that: the first power unit includes a first battery pack for rotating the first motor; and the second power unit includes a second battery pack for rotating the second motor. a first power unit; and a second power unit, wherein the first power unit includes: a first hydraulic pump for pressure-transporting the hydraulic oil; a first motor for driving the first hydraulic pump; and a first fluid passage (e) for pressure-transporting the hydraulic oil from the first hydraulic pump to the electric tool head, a first hydraulic pump for pressure-transporting the hydraulic oil; a first motor for driving the first hydraulic pump; and a first fluid passage (e) for pressure-transporting the hydraulic oil from the first hydraulic pump to the electric tool head, and wherein the second power unit includes: a second hydraulic pump for pressure-transporting the hydraulic oil; a second motor for driving the second hydraulic pump; and a second fluid passage (f) for pressure-transporting the hydraulic oil from the second hydraulic pump to the electric tool head; a second hydraulic pump for pressure-transporting the hydraulic oil; a second motor for driving the second hydraulic pump; and a second fluid passage (f) for pressure-transporting the hydraulic oil from the second hydraulic pump to the electric tool head; the power unit further comprising: a converging joint for converging the first fluid passage (e) and the second fluid passage (f); a pressure restricting device arranged between the converging joint and the first hydraulic pump to restrict rise in pressure in the first fluid passage (e); and a returning device arranged between the converging joint and the second hydraulic pump to drain the hydraulic oil from the second fluid passage (f) and thereby enable return operation of the piston, a converging joint for converging the first fluid passage (e) and the second fluid passage (f); a pressure restricting device arranged between the converging joint and the first hydraulic pump to restrict rise in pressure in the first fluid passage (e); and a returning device arranged between the converging joint and the second hydraulic pump to drain the hydraulic oil from the second fluid passage (f) and thereby enable return operation of the piston, wherein the power unit pressure-transports the hydraulic oil from the converging joint to the electric tool head to drive the electric tool head; characterised in that: the first power unit includes a first battery pack for rotating the first motor; and the second power unit includes a second battery pack for rotating the second motor. the first power unit includes a first battery pack for rotating the first motor; and the second power unit includes a second battery pack for rotating the second motor.