Provided is a preserving agent for organs or tissue that includes (A) quercetin and (B) at least one type of sugar selected from the group consisting of fructose and sucrose. Also provided is a preservation method for organs or tissue including a step in which organs or tissue are immersed in a liquid mixture including: a preservation liquid for organs or tissue including the preserving agent； (A) quercetin； and (B) at least one type of sugar selected from the group consisting of fructose and sucrose.
