An electrical caulking gun has a gun body and a clutching device. The clutching device has a clutching switch, a linking lever, a clutching block and a block spring. The clutching switch is mounted on the gun body and has a pressed segment and a pushing segment having an inclined pushing surface. The linking lever is pivotally mounted in the gun body and has an abutting end and a pushing end. The abutting end abuts with the pushing surface of the clutching switch. The clutching block has an inclined pushed surface and an engaging rod. The engaging rod detachably engages a transmission device of the caulking gun. The block spring provides a force to push the engaging rod on the clutching block to engage the transmission device.