To reduce pressure loss of intake air of a venturi type mixer.

This venturi type mixer 30 is equipped with a fuel gas supply pipe 13 and an exhaust gas supply pipe 16, a barrel part 19 in which an internal space 20 passing intake air 27 is arranged is connected to an intake pipe 7 on the intake air side of an engine, an inner wall 21 whose cross section along the flow direction of the intake air 27 is formed into a hourglass shape from an intake air inflow side toward an intake air outflow side is arranged in the inside of the internal space 20, a space 24 into which fuel gas 10 and exhaust gas 15 are led to flow and a hourglass-shaped space 25 in which intake air 27 flows are formed between the inner wall 21 and the inside of the barrel part 19, and an ejection hole 26 through which fuel gas 10 and exhaust gas 15 are ejected to the hourglass-shaped space 25 is arranged in the part of the inner wall 21 where the hourglass-shaped space 25 is narrowed down.