To provide a water level adjustment device of a washing machine which accurately senses the level of water in a washing drum by use of a piezoelectric film sensor and which has a simple structure.

In a water level adjustment device comprising a piezoelectric film sensor 32 connected to a water drum and changing its output signal in proportion to a force applied to the surface of the sensor, an amplifying part 33 amplifying the signals output from the piezoelectric film sensor 32, a control part 30 controlling the level of water according to water level data, a water feed valve driving part 35 controlling the operation of a water feed valve 34, and a drain valve driving part 37 controlling the operation of a drain valve 36, the piezoelectric film sensor 32 having a high measuring accuracy and being excellent in reaction to stimuli is used to accurately detect the level of water, and is directly mounted in the water drum to provide a simplified structure.