A seal device fixed to an end portion of a slider of a guide device includes: a casing; a plurality of seal members; and elastic members, wherein each seal member has a recess portion in which a rail penetrates. An inner circumferential face of the recess portion comes into contact with an outer surface of the rail when the seal member is pushed onto one side of the rail by the elastic members. The plurality of seal members are arranged in the casing in such a manner that when a seal portion of one seal member is pushed by the elastic member and contacted with one side of the rail, a seal portion of the next seal member is pushed by the elastic member and contacted with the other side of the rail.