A flush toilet to be cleaned by pressurized flush water, said flush toilet comprising: a toilet main unit provided with a bowl portion, a rim water spouting port and jet water spouting port both for expelling flush water, and a drain trap pipe; a reservoir tank for storing flush water; rim spout water supply means for supplying flush water to the rim water spouting port at a predetermined timing; reservoir water supply means for supplying flush water to the reservoir tank at a predetermined timing; a pressurizing pump for pressurizing flush water stored in the reservoir tank and supplying the flush water to the jet water spouting port; and wherein the drain trap pipe includes an inlet portion, a trap ascending pipe rising from the inlet portion, and a trap descending pipe dropping from the trap ascending pipe; the jet water spouting port is disposed approximately horizontally, pointing toward the inlet portion of the drain trap pipe; wherein the flush toilet further comprises: a pressurizing pump control means for controlling the operation of the pressurizing pump and the rpm thereof so as to control the flow speed and the flow volume of flush water spouted from the jet water spouting port; wherein the pressurizing pump control means is configured to control the rpm of the pressurizing pump so that a first flow volume for generating a siphon effect is spouted from the jet water spouting port, characterised in that the pressurizing pump control means is configured to control the rpm of the pressurizing pump so that a second flow volume, which is smaller than the first flow volume, is spouted, prior to the end of the siphon effect generated by the first flow volume, from the jet water spouting port after the first flow volume is spouted, so as to generate a flow speed capable of conveying waste, and in such a way as to seal a cross section at some location of the drain trap pipe, thereby continuing the siphon effect. a toilet main unit provided with a bowl portion, a rim water spouting port and jet water spouting port both for expelling flush water, and a drain trap pipe; a reservoir tank for storing flush water; rim spout water supply means for supplying flush water to the rim water spouting port at a predetermined timing; reservoir water supply means for supplying flush water to the reservoir tank at a predetermined timing; a pressurizing pump for pressurizing flush water stored in the reservoir tank and supplying the flush water to the jet water spouting port; and wherein the drain trap pipe includes an inlet portion, a trap ascending pipe rising from the inlet portion, and a trap descending pipe dropping from the trap ascending pipe; the jet water spouting port is disposed approximately horizontally, pointing toward the inlet portion of the drain trap pipe; wherein the flush toilet further comprises: a pressurizing pump control means for controlling the operation of the pressurizing pump and the rpm thereof so as to control the flow speed and the flow volume of flush water spouted from the jet water spouting port; wherein the pressurizing pump control means is configured to control the rpm of the pressurizing pump so that a first flow volume for generating a siphon effect is spouted from the jet water spouting port, a pressurizing pump control means for controlling the operation of the pressurizing pump and the rpm thereof so as to control the flow speed and the flow volume of flush water spouted from the jet water spouting port; wherein the pressurizing pump control means is configured to control the rpm of the pressurizing pump so that a first flow volume for generating a siphon effect is spouted from the jet water spouting port, characterised in that the pressurizing pump control means is configured to control the rpm of the pressurizing pump so that a second flow volume, which is smaller than the first flow volume, is spouted, prior to the end of the siphon effect generated by the first flow volume, from the jet water spouting port after the first flow volume is spouted, so as to generate a flow speed capable of conveying waste, and in such a way as to seal a cross section at some location of the drain trap pipe, thereby continuing the siphon effect.