An anesthetic vaporizer is disclosed herein which comprises a fresh gas inlet, a mixed gas outlet, a first gas branch circuit, a second gas branch circuit and a vaporizing chamber. The vaporizing chamber has a reservoir for containing an anesthetic agent. The first gas branch circuit connects the fresh gas inlet and the mixed gas outlet. The second gas branch circuit comprises a first pneumatic circuit, a pressure compensation unit, a second pneumatic circuit, a wick unit and a third pneumatic circuit. The pressure compensation unit has a curved, continuous and sealed vent slot. The wick unit has an immersion portion which is directly contacted with the anesthetic agent in the reservoir. The fresh gas inlet, the first pneumatic circuit, the vent slot, the second pneumatic circuit, the wick unit, the third pneumatic circuit and the mixed gas outlet are sequentially connected with one another. The pressure compensation unit is provided in the reservoir and has a heat conductor which is directly contacted with the anesthetic agent to transfer heat. The vent slot is formed in the heat conductor. The anesthetic vaporizer according to the invention can stabilize the concentration of the anesthetic vapor in the outputted mixed gas.
