There is provided an engine water-cooling device that can increase warming-up efficiency of an engine. The engine water-cooling device includes a thermostat housing that houses a thermostat. The thermostat housing is mounted to a front wall of a cylinder head in one side portion in a width direction of the cylinder head. A cooling water pump is mounted to a front wall of a cylinder block in a central portion in a width direction of the cylinder block. A bypass passage includes an intra-head bypass passage in the cylinder head, and the intra-head bypass passage includes a width-direction passage portion extending from a position behind the thermostat housing to a position behind and above the cooling water pump.