A method for processing coffee beans (C), including the step of charging the coffee beans (C) in a vessel ( 10 ) and supplying water inside a vessel body ( 11 ) by spraying out water inside the vessel body ( 11 ) through an injection liquid charging channel ( 23 ) via a spray nozzle ( 23 a) for allowing water to penetrate to the inside of the coffee beans (C) while the inside of the vessel body 11 is under pressure and heated, and the step of reducing the pressure inside the vessel body ( 11 ) for water having penetrated to the inside of the coffee beans (C) to expand by vaporization in grinding the coffee beans (C) that have been swollen in a porous manner using an expanding force.
