A vertical multicylinder straight engine, comprising: a cylinder block around a plurality of cylinder barrels, the cylinder block allowing engine cooling water to pass through a cylinder jacket, wherein the plurality of cylinder barrels include a front-end barrel, a rear-end barrel, and middle barrels (B2, B3) disposed between these two barrels, taking a direction along which a crankshaft central axis line extends as a front-rear direction, and a side of a flywheel as a rear side, a jacket inlet for introducing the engine cooling water supplied from a radiator into separated channels for diverting the engine cooling water in the front-rear direction; a plurality of separated outlets (b1-b4) for diverting the engine cooling water diverted in the front-rear direction toward the respective cylinder barrels; and the cooling water jacket comprising heat dissipator channels for dissipating heat of the respective cylinder barrels to the engine cooling water introduced through the separated outlets, and the plurality of separated outlets include: a front-side separated outlet to the front-end barrel; a rear-side separated outlet to the rear-end barrel; and middle separated outlets (b2, b3) to the middle barrels (B2, B3) between the front-end barrel and the rear-end barrel, wherein the jacket inlet is disposed so as to be contained within an entire middle barrel side area, wherein the entire middle barrel side area is lateral to the middle barrels (B2, B3) and has a front-rear length as long as a length from a front-most end to a rear-most end of the middle barrels (B2, B3), characterised in that the vertical multicylinder straight engine comprises an intermediary water channel between the radiator and the jacket inlet, wherein an entire amount of the engine cooling water from the radiator is supplied to the jacket inlet via the intermediary water channel, and an oil cooler is disposed within the intermediary water channel. a cylinder block around a plurality of cylinder barrels, the cylinder block allowing engine cooling water to pass through a cylinder jacket, wherein the plurality of cylinder barrels include a front-end barrel, a rear-end barrel, and middle barrels (B2, B3) disposed between these two barrels, taking a direction along which a crankshaft central axis line extends as a front-rear direction, and a side of a flywheel as a rear side, a jacket inlet for introducing the engine cooling water supplied from a radiator into separated channels for diverting the engine cooling water in the front-rear direction; a plurality of separated outlets (b1-b4) for diverting the engine cooling water diverted in the front-rear direction toward the respective cylinder barrels; and the cooling water jacket comprising heat dissipator channels for dissipating heat of the respective cylinder barrels to the engine cooling water introduced through the separated outlets, and the plurality of separated outlets include: a front-side separated outlet to the front-end barrel; a rear-side separated outlet to the rear-end barrel; and middle separated outlets (b2, b3) to the middle barrels (B2, B3) between the front-end barrel and the rear-end barrel, wherein the jacket inlet is disposed so as to be contained within an entire middle barrel side area, wherein the entire middle barrel side area is lateral to the middle barrels (B2, B3) and has a front-rear length as long as a length from a front-most end to a rear-most end of the middle barrels (B2, B3), characterised in that the vertical multicylinder straight engine comprises an intermediary water channel between the radiator and the jacket inlet, wherein an entire amount of the engine cooling water from the radiator is supplied to the jacket inlet via the intermediary water channel, and an oil cooler is disposed within the intermediary water channel.