An engine cooling structure for cooling an engine body including a plurality of cylinders arranged in a row by using a coolant, the engine cooling structure comprising: a cylinder block including: a block inner peripheral wall defining the plurality of cylinders; and a block outer peripheral wall surrounding the block inner peripheral wall to define a water jacket through which the coolant circulates between the block outer peripheral wall and the block inner peripheral wall; and a spacer housed in the water jacket, wherein the block outer peripheral wall includes a coolant inlet configured to introduce the coolant from a water pump into the water jacket at one end in a cylinder row direction, the spacer includes: a peripheral wall surrounding the block inner peripheral wall to divide the water jacket into an inner space near the plurality of cylinders and an outer space far from the plurality of cylinders; a dividing wall provided along a circumferential direction of the peripheral wall to divide the peripheral wall into an upper peripheral wall and a lower peripheral wall below the upper peripheral wall; and a distribution wall provided in a part facing the coolant inlet of the peripheral wall in order to distribute the coolant introduced from the coolant inlet into the water jacket to a first side and a second side in the circumferential direction of the peripheral wall, the dividing wall includes a part protruding outward from the peripheral wall at a position between a lower end and an upper end of the coolant inlet, and the distribution wall includes: an upper distribution wall extending upward from an upper surface of the dividing wall; and a lower distribution wall extending downward from a lower surface of the dividing wall, characterized in that the distribution wall is configured to protrude outward from the peripheral wall and extend in an up-and-down direction, the cylinder block includes a coolant exit (16, 17), constituting a part of an auxiliary passage (L20, L30), the coolant exit (16, 17) being provided at a position facing the lower peripheral wall, the coolant exit (16, 17) being configured to lead the coolant in the water jacket outside the cylinder block, and the coolant exit (16, 17) is connected to a heat exchanger (62 to 65) provided outside the engine body. a cylinder block including: a block inner peripheral wall defining the plurality of cylinders; and a block outer peripheral wall surrounding the block inner peripheral wall to define a water jacket through which the coolant circulates between the block outer peripheral wall and the block inner peripheral wall; and a spacer housed in the water jacket, wherein the block outer peripheral wall includes a coolant inlet configured to introduce the coolant from a water pump into the water jacket at one end in a cylinder row direction, the spacer includes: a peripheral wall surrounding the block inner peripheral wall to divide the water jacket into an inner space near the plurality of cylinders and an outer space far from the plurality of cylinders; a dividing wall provided along a circumferential direction of the peripheral wall to divide the peripheral wall into an upper peripheral wall and a lower peripheral wall below the upper peripheral wall; and a distribution wall provided in a part facing the coolant inlet of the peripheral wall in order to distribute the coolant introduced from the coolant inlet into the water jacket to a first side and a second side in the circumferential direction of the peripheral wall, a peripheral wall surrounding the block inner peripheral wall to divide the water jacket into an inner space near the plurality of cylinders and an outer space far from the plurality of cylinders; a dividing wall provided along a circumferential direction of the peripheral wall to divide the peripheral wall into an upper peripheral wall and a lower peripheral wall below the upper peripheral wall; and a distribution wall provided in a part facing the coolant inlet of the peripheral wall in order to distribute the coolant introduced from the coolant inlet into the water jacket to a first side and a second side in the circumferential direction of the peripheral wall, the dividing wall includes a part protruding outward from the peripheral wall at a position between a lower end and an upper end of the coolant inlet, and the distribution wall includes: an upper distribution wall extending upward from an upper surface of the dividing wall; and a lower distribution wall extending downward from a lower surface of the dividing wall, characterized in that the distribution wall is configured to protrude outward from the peripheral wall and extend in an up-and-down direction, the cylinder block includes a coolant exit (16, 17), constituting a part of an auxiliary passage (L20, L30), the coolant exit (16, 17) being provided at a position facing the lower peripheral wall, the coolant exit (16, 17) being configured to lead the coolant in the water jacket outside the cylinder block, and the coolant exit (16, 17) is connected to a heat exchanger (62 to 65) provided outside the engine body.