A portable cutting tool , whereby the portable cutting tool comprises: a blade ; a motor for driving the blade to rotate, wherein the motor comprises an output shaft; a cutting unit comprising a guard assembly; wherein the guard assembly comprises an upper guard for receiving the blade and a lower guard , wherein the lower guard is rotatable relative to the upper guard to expose the blade to cut a workpiece ; a base connected to the upper guard, wherein the base is provided with a blade through-hole for the blade to pass through, and further comprises a base bottom portion for abutting against the workpiece and a front side wall extending upwards from the base bottom portion; a housing , comprising a front portion connected to the upper guard, a rear portion extending longitudinally, and a gripping portion disposed between the front portion and the rear portion, wherein the blade is rotatably disposed on the front portion by a blade shaft , the motor is disposed in the rear portion, and the blade shaft is perpendicular to the output shaft; and a supporting member connected to the base, the housing and the cutting unit movable around a first axis relative to the base and the supporting member to change the cutting depth, and the supporting member comprising a depth adjusting holder , wherein the depth adjusting holder is provided with a first guide slot which is an arc-shaped guide slot, and the center of a circle corresponding to the arc where the first guide slot is located is on the first axis , wherein the upper guard and the arc-shaped guide slot are respectively disposed on two sides of the front portion. a blade ; a motor for driving the blade to rotate, wherein the motor comprises an output shaft; a cutting unit comprising a guard assembly; wherein the guard assembly comprises an upper guard for receiving the blade and a lower guard , wherein the lower guard is rotatable relative to the upper guard to expose the blade to cut a workpiece ; a base connected to the upper guard, wherein the base is provided with a blade through-hole for the blade to pass through, and further comprises a base bottom portion for abutting against the workpiece and a front side wall extending upwards from the base bottom portion; a housing , comprising a front portion connected to the upper guard, a rear portion extending longitudinally, and a gripping portion disposed between the front portion and the rear portion, wherein the blade is rotatably disposed on the front portion by a blade shaft , the motor is disposed in the rear portion, and the blade shaft is perpendicular to the output shaft; and a supporting member connected to the base, the housing and the cutting unit movable around a first axis relative to the base and the supporting member to change the cutting depth, and the supporting member comprising a depth adjusting holder , wherein the depth adjusting holder is provided with a first guide slot which is an arc-shaped guide slot, and the center of a circle corresponding to the arc where the first guide slot is located is on the first axis , wherein the upper guard and the arc-shaped guide slot are respectively disposed on two sides of the front portion. <EOS>