This study introduces a gait analysis system using a pair of slippers with flexible piezoelectric sensors. We install only one flexible sensor based on polyvinylidene fluoride, which is a flexible piezoelectric material, in each slipper. The flexible sensor is positioned in the slipper sole area under the inner arch of the foot. In this position, the sensor undergoes bending for walking, and generates electrical signals through the piezoelectric characteristic. We focus on the detection of the heel strike and toe-off moments from the sensor output. We then acquire the floor contract information of the slippers from the detection and extract eight gait parameters. We develop a gait analysis system including the sensing slippers, a sensing module for data collection and wireless communication, and an external computer with the data processing program. Moreover, we demonstrate that the proposed total gait analysis system based on the slippers with the flexible piezoelectric sensors works efficiently.