PROBLEM TO BE SOLVED: To provide a gel medium for cultivating plants that makes it possible to cultivate plants well at low cost without using soil, and a method of cultivating plants.SOLUTION: Use of a gel medium containing an iota type carrageenan as a gel base enables plant roots to spread well. That is, a plant-cultivation gel medium containing the iota type carrageenan is provided to enable plants to be cultivated well at low cost without use of soil. The plant-cultivation gel medium further containing minerals including at least iron is also provided. Further, a method of cultivating plants including the sowing of seeds in the plant-cultivation gel medium is provided.