The impeller structure of blower in the present invention mainly includes a hub and an impeller. The hub has a spindle disposed centrally therein. The impeller has a top connection ring, a bottom connection ring, a pressure-retaining ring and a plurality of blades, in which the blades are vertically arranged around the periphery of the hub, an outer edge on a top side of each blade is connected with a top connection ring, an bottom side of the inner side of the blade is connected with a bottom connection ring, the outer side is connected with the pressure-retaining ring, and a plurality of swirl-like ribs are extended outwards from the bottom edge of the periphery of the hub and connected with the bottom connection ring. At least a pressure relief hole is provided between the pressure-retaining ring and the bottom connection ring so that the bottom surface of the impeller is not fully enclosed. Therefore, the pressure relief hole is located on a space between the pressure-retaining ring and the bottom connection ring. When air passes through the pressure relief hole, a pressure effect is generated so as to increase air pressure and air volume of blower and alleviate the chance of turbulence. The pressure-retaining ring also has the effect of reinforcing the blade strength.