An adhesive seal member for a fuel cell of the present invention includes a cross-linked product of a rubber composition containing components to : at least one rubber component selected from ethylene-propylene rubber and ethylene-propylene-diene rubber, an organic peroxide having a one-hour half-life temperature of 130\xb0 C. To manufacture a liquid-crystalline polymer having 50 mol % or larger ratio of constitutive unit introduced from 4-hydroxybenzoic acid, the reaction is conducted under the presence of an acylating agent and of a catalyst quantity of aromatic sulfonic acid. The removable aft member is preferably composed of stainless steel and preferably has a fang-like shape. The system controls the degree of charge neutralization of the sample based on the result of the measurement, or estimates or calculates an electric potential distribution appearing on a front surface of the sample and obtained when the sample is placed on the sample holder or the like. A device for implementing such a checking method is also described.