A process of manufacturing the spark plug that includes a step in which a receiving die having an insertion hole and a taper portion is used, wherein a thread portion of the spark plug is inserted into the insertion hole and a seat portion of the spark plug is brought into contact with the taper portion, and a pressing force is applied to a rear end portion of a metallic shell of the spark plug so as to bend a rear end opening portion of the metallic shell, and to thereby form a crimped portion, whereby an insulator and the metallic shell are fixed together.