A blade clamping device includes a driving shaft and a base member fixedly mounted to the driving shaft. An opening is defined in the base member and a blade is inserted in the base member and connected to the driving shaft. A cam member is pivotably engaged with the opening of the base member and a cam head contacts a side of the blade. The base member is received in a casing which is connected to the electric saw and an opening is defined in the casing. A lever is pivotably engaged with the opening of the casing and includes a pushing end which is located beneath a bar of the cam member so that when pivoting the lever, the pushing end pivots the cam member to remove the cam head from the blade.