A filter unit for a canister, which is disposed in a canister and removes foreign substances or powder in air flowing into or discharged from an air port may include a main filter that is a plate connected in a ring shape between an air port and activated carbon to pass air laterally, and configured to filter foreign substances or powder in air, and a top cover thermally bonded to a top of the main filter and configured to transversely distribute air flowing inside through the air port.