An oil passage structure for an engine of a vehicle is provided with a connecting rod swingably coupled to a crankshaft rod by a plurality of crankpins, the plurality of crankpins being disposed between a plurality of crank journals, and a plurality of support portions for rotatably supporting the crankshaft by the plurality of crank journals in a cylinder block. The crankshaft has a first oil passage formed therein, the first oil passage supplying oil from an opening formed in one end face thereof to sliding surfaces of the plurality of crankpins, the plurality of support portions have a second oil passage formed therein, the second oil passage supplying the oil to a sliding surface of each of the plurality of crank journals, and the first oil passage and the second oil passage communicate with each other in some of the support portions and in some of the crank journals.