An ultrasonic velocity profile monitor (UVP) measurement was performed to measure the average liquid velocity field around a large bubble rising in stagnant water in a round pipe of inner diameter D=54mm in order to obtain fundamental information for gas-liquid two-phase slug flows. Two ultrasonic transducers were set at different directions to obtain velocity vectors. The measured results are presented and compared with the results of some previous studies on the corresponding phenomena. In the liquid film near the bubble nose, the difference in bubble length does not affect the acceleration. The parameter z/D is more dominant than z itself, particularly when z/D is less than unity. In the wake region, a large ring vortex is recognized. The upward velocity at the pipe axis agrees well with previously predicted results. The effect of bubble length on the vortex length is also discussed.