Abstract: To provide an artificial annulus sizing tool capable of determining a suitable size for an artificial annulus to be implanted in a patient. [Solution] An artificial annulus sizing tool comprising an annular core material and a cover material covering the core material to a predetermined thickness, the cover material portion being attached to the annulus using suturing thread for implanting artificial annuli, and the part of the cover material engaged with the suturing thread being broken after a suitable artificial annulus size is determined for the annulus, allowing for removal from the suturing thread.