This invention provides an elastic member for a methanol fuel cell cartridge, comprising an elastomer having a compression set of 1 to 80 and a hardness (type A) of 40 to 70 and having an operating limit time of 10,000 hours or more determined by a DMFC performance test for the fuel cell. The elastic member can prevent leakage of methanol from a methanol fuel cell cartridge, or a connection part between the cartridge and a fuel cell body and, at the same time, can realize long-term operation of the fuel cell without causing deterioration of power generation performance.