The invention discloses a circular cutting device. The circular cutting device comprises a supporting part, a driving part and a cutting part, wherein the supporting part comprises a base and a supporting rod; a plurality of magnets and a telescopic positioning needle are arranged at the bottom of the base; the driving part comprises a speed-change gear, arranged on the supporting rod, a motor, abattery and a shifting rod; the speed-change gear is engaged with a driving gear; the driving gear is connected with the motor and the battery; the shifting rod is arranged on the lower portion of thespeed-change gear; the cutting part comprises a fixed rod, an adjustable scale rod and a welding gun fixing clamp; a cutting head is arranged at one end of the adjustable scale rod; the adjustable scale rod is connected with a welding gun through the welding gun fixing clamp; the fixed rod is parallel to the adjustable scale rod; the inner end of the fixed rod is connected with the supporting rod; the outer end of the fixed rod is connected with the adjustable scale rod through an adjusting clamp; and the lower end of the shifting rod is lower than the outer end of the fixed rod. The circularcutting device can replace manual operation, the cutting time and the size of a cut circular workpiece can be adjusted as required, and the smooth cutting surface meets the workpiece standard.