Characteristics of shock phenomena in a one-component two-phase bubbly flow induced by a sudden valve closure at the downstream end of a test section are investigated. An experiment was conducted for a two-phase flow in a horizontal stainless tube of 21.4mm Id and 16.17m length with a surge tank having a gas chamber at the upstream end, using Freon-113 as the working fluid. The pressure transients are presented and discussed qualitatively. They are different from those of a two-component two-phase flow due to the mass transfer between the vapor and the liquid. The effect of factors such as the initial void fraction, the liquid velocity, the initial pressure, and the valve closing time on the profiles of the transient pressure are shown. Also, the behaviors of the vapor bubbles after the valve closure are sketched and explained, comparing with the profiles of transient pressure.