<;P>;PROBLEM TO BE SOLVED: To provide a preparing method of a decellularized living organism tissue which can inhibit calcification, a washing liquid used for the preparing method of the decellularized living organism tissue, and a transplantation piece having the decellularized living organism tissue. <;P>;SOLUTION: An isolated cell in a living organism tissue is broken, and then the broken cell in the living organism tissue is removed by a buffer solution containing 2.0 mmol/L or less of phosphoric ions and including one or more compounds selected from a group comprising citric acid, ethylenediaminetetraacetic acid, and their salts which are allowed physiologically. <;P>;COPYRIGHT: (C)2011,JPO&INPIT