Provided is a method for carburizing a tantalum container which can easily control the carburization thicknesses of various portions of the tantalum container and carburize the tantalum container with a uniform thickness. A method for carburizing a tantalum container 1 made of tantalum or a tantalum alloy to allow carbon to penetrate the tantalum container 1 includes the steps of: supporting the tantalum container 1 on a support member 5, 6 provided in a chamber 3 and setting the tantalum container 1 in the chamber 3; and reducing the pressure inside the chamber 3 and heating the interior of the chamber 3, wherein a carbon source is placed in the vicinity of a portion of the tantalum container 1 hard to carburize.