In a V-type six cylinder engine, cylinder groups are provided in which a plurality of cylinders are arranged divided into left and right first and second banks (12, 13). An intake pipe (51), as well as a first exhaust pipe (57) and a second exhaust pipe (58), are connected to the cylinder groups of the banks (12, 13). A first upstream three-way catalyst (59) and a first control valve (64) are provided in one exhaust pipe (57) while a second upstream three-way catalyst (60) and a second control valve (65) are provided in the other exhaust pipe (58). The exhaust pipes (57, 58) are communicated together upstream of the upstream three-way catalysts (59, 60) and the control valves (64, 65) by a communicating pipe (63). A third control valve (66) that adjusts the flowrate of exhaust gas is provided in the communicating pipe (63).