Provided are a source gas supply unit capable of supplying a constant amount of source gas to a deposition chamber to deposit a uniform layer, and a deposition apparatus and method using the same. The source gas supply unit includes a canister in which a source is stored, a heater heating the canister, a source gas supply pipe provided on one side of the canister, a measuring unit installed on the source gas supply pipe and measuring an amount of source gas passing through the source gas supply pipe, and a temperature controller connected to the heater and the measuring unit. The temperature controller controls the heater based on the amount of the source gas measured by the measuring unit.