To provide a sealing material cutting support tool which can cut a sealing material in a desired shape without damaging a body to which the tool is applied even if the body is formed of a soft material and which can be easily fixed and removed, and also provide a method of cutting a sealing material.

This sealing material cutting support tool used for cutting a sealing material charged in the joint part of the body which the tool is applied using a cutter includes a long body part, a contact part which is provided to the body part in the longitudinal direction and slits the sealing material by bringing the cutter into contact therewith, and a penetration part which comprises a sharp front end shape and is penetrated into the sealing material to be cut to hold the position of the contact surface.