A lavatory pan washing apparatus includes a water supply unit supplying washing water into a rim so that a whirling flow is formed in a lavatory bowl, an air inlet pipe connected to a water discharge channel continuing to the downstream side of a water sealing portion of a pan, an air sucking unit sucking air through the pipe from the channel, and a control unit configured to activate the water supply unit at a time of washing of the pan so that the washing water is supplied into the water sealing portion. The control unit is configured to start activation of the air sucking unit after rise of a water level in the lavatory bowl, so that air is sucked through the pipe from the channel. The control unit is configured to deactivate the water supply unit after air has flowed through the air inlet pipe into the channel.