A wet type exhaust gas desulfurization method includes sucking liquid in a liquid reservoir containing a sulphur compound formed from sulphur dioxide contained in exhaust gas so as to form a flow of the liquid, reducing the flow of the liquid in diameter to form a depressurized region in the flow, the reducing including passing the liquid through a reduction section which includes a reduction section plate having a reduction section hole and a peripheral portion surrounding the reduction section hole, the peripheral portion protruding toward the upstream side of the flow, introducing air into the depressurized region so as to generate a mixture stream of the air and the liquid, and spouting the mixture stream into the liquid reservoir. The reducing includes forming cavities in the flow, the forming cavities includes shearing the flow, and the shearing includes bringing the flow into contact with the peripheral portion.