Abstract: A method of improving germination of plant seeds, comprising a low temperature contact process of allowing plant seeds to contact plant growth regulating agents and water at a temperature lower than 10° C. wherein the treatment time in the low temperature contact process is shorter than 24 hours, and a method of improving germination of plant seeds, comprising (1) a low temperature contact process of allowing plant seeds to contact plant growth regulating agents and water at a temperature lower than 10° C., and (2) a low temperature preservation process of preserving, after the first process, the plant seeds at a temperature lower than 10° C., wherein the sum of the treatment time in the low temperature contact process and the treatment time in the low temperature preservation process is shorter than 24 hours; and the like.