To provide an ultrasonic cleaning apparatus capable of preventing the contact of an ultrasonic cleaning unit with an object to be washed.

The ultrasonic cleaning apparatus is equipped with an ultrasonic cleaning unit 40 opposedly arranged to the surface Wa to be cleaned of the object W to be washed and a positioning mechanism 30 for positioning the ultrasonic cleaning unit 40. The ultrasonic cleaning unit 40 has an ultrasonic diffusion body 62 which has an ultrasonic transducer 63 fixed to one surface thereof and is arranged in opposed relation to the surface of the object W to be washed on the other surface thereof and the non-contact distance sensor 71 for measuring the relative distance between the ultrasonic diffusion body 62 and the surface Wa to be washed. The positioning mechanism 30 has a control circuit 32 for positioning the ultrasonic cleaning unit 40 so as to hold the distance between the ultrasonic diffusion body 62 and the surface Wa to be washed.