Abstract: A crankshaft supporting device for a multi-cylinder engine including a plurality of bulkheads provided in a cylinder block of the engine to be arranged along an axis of the crankshaft, disposed in a lower part of the cylinder block. A bearing cap member has a plurality of bearing cap portions each coupled with a lower end of one of the bulkheads so as to constitute a bearing portion for supporting the crankshaft in conjunction with the bulkhead, and a pair of beam portions extending along the axis of the crankshaft to interconnect therethrough two adjacent bearing cap portions. A reinforcement member has a side wall portion which is coupled with a skirt portion of the cylinder block, and a plurality of bolt seats are located underneath the beam portion of the bearing cap member. A plurality of ribs interconnect at least one of the bolt seats and at least one of the side wall portions. A plurality of bolts fasten the beam portions with the bolt seats.