This article presents an analytic investigation to calculate the width of the shock in pair plasma. A solitary electromagnetic wave is propagated obliquely in the plasma where the wave direction is characterized by a propagation angle from direction of a background (constant) magnetic field. Based on Sagdeev method, the shock wave is determined by oscillation of pseudo--particle in pseudo--potential well. It is shown that for any fixed value of the propagation angle, the width of the shock becomes an explicit function of Alfe'vn Mach number of plasma. Graphs of the width of the shock versus Mach number represent a rapid montonous decreasing functions.
