To make the clogging of an exhaust trap hardly generable and to make increasable the collecting efficiency of solid substance.

This exhaust trap has six trap elements 61(1) to 61(6), a storing case 62, a cooling flange 63 and a fixing bolt 64, where the trap elements 61(1) to 61(6) have functions of collecting reaction products. The storing case 62, the cooling flange 63 and the fixing bolt 64 have functions of holding the trap elements 61(1) to 61(6). The trap elements 61(a) (a=1, 2) 61(b) (b=3, 4), 61(5) and 61(6) have different collecting efficiency. They are arranged in such a manner that the collecting efficiency is made higher as it goes from the upstream side to the downstream side of the flow of the exhaust gas.