Provided are: a method for preparing a decellularized tissue product in which decellularized tissue can be filled with liquid while changes in the structure of support tissue constituting the decellularized tissue are inhibited； and a graft provided with a decellularized tissue product. The method for preparing a decellularized tissue product includes a reduced-pressure step for bringing an animal-derived decellularized tissue material and a liquid into contact under reduced-pressure conditions, and/or a pressurized step for bringing same into contact under pressurized conditions. The graft is provided with a decellularized tissue product prepared by the method of preparation.
