The invention discloses a high temperature and high pressure steam cleaning machine comprising a spray gun and a nozzle. The nozzle is a flat nozzle, the nozzle comprises a flow equalizing device, a flow dividing device and an outflow device, the flow equalizing device comprises a pressure equalizing chamber, a plurality of flow equalizing channels and a plurality of pressure equalizing outlets, the flow equalizing channels enable all pressure equalizing outlets to be connected to the pressure equalizing chamber, the pressure equalizing chamber is connected with an outlet of the spray gun, thelengths of the respective channels are the same, the pressure equalizing chamber is a spherical closed cavity, the flow equalizing channels communicate to the surface of the pressure equalizing chamber through holes, the holes are evenly arranged in the surface of the pressure equalizing chamber, and the pressure equalizing outlets are linearly and evenly distributed on the outside of the flow equalizing device. The air pressure sprayed by the spray gun is evenly distributed into the flow equalizing channels through the pressure equalizing chamber, and paths of all the flow equalizing channels are the same, so that steam flow sprayed from the pressure equalizing outlets is the same, when fluid passes through the flow dividing device and the outflow device to be sprayed out from the flat nozzle, steam flow sprayed out from the side portions and the middle portion is more uniform, and a user can more quickly remove large-area dirt.