Some observed astrophysical phenomena such as the blast of a supernova (cf. Zeldovich and Novikov, 1966; Blandfordet al., 1977; Shapiro, 1979) suggest the necessity of study of the motion of shock waves in a relativistic fluid flow in the presence of a magnetic field. This paper deals with the motion of special relativistic shock wave which propagates from the center line outwardly after an explosion with the assumption that the magnetic field which has an axial component only. Similarity solutions which depend on the parameter ξ=r/t are constructed. Two special cases are then studied in detail. In the first case, there is an ultra-relativistic fluid in front of the shock and in the second case, there is a cold fluid in front of the shock.