In a pan coating apparatus (10) including a rotary drum (1) which rotates about a horizontal rotation axis (O), an air supply chamber (13) having a larger sectional area than that of an opening portion (7) is arranged on a front stage with respect to the front-surface opening portion (7) of the rotary drum. The air supply chamber (13) is formed in a chamber door (11) attached to a front of a casing (2), and has one end side communicating to the opening portion (7) and another end side connected to an air supply duct (19) via an air supply hole (18). The air flowing into the air supply chamber (13) from the air supply duct (19) is reduced in flow rate in the air supply chamber (13) and supplied from the opening portion (7) into the rotary drum (1) with the air flow thereof in a stable state.
