Preservative agent for use in low-temperature preservation of biological material, and method for preserving biological material at low temperature

Disclosed are: a preservative agent for use in the low-temperature preservation of a biological material, which comprises a compound represented by formula (I); a preservative solution for use in the low-temperature preservation of a biological material, which contains the preservative agent; and a method for preserving a biological material, which is characterized by soaking the biological material in a solution containing a compound represented by formula (I) and keeping the solution at a low temperature.