This thesis describes a procedure of ultrasonic measurement of wall thickness. The thesis consists of theoretical part and an experimental part. In the theoretical part, the non-destructive methods of testing which are currently being used in industry are described, with an emphasis on the ultrasonic testing. Ultrasonic testing is further described. The basics of the ultrasonic measurement, the working principle and the equipment which is used are all explained. In the experimental part, the ultrasonic measurement of wall thickness is described. The ultrasonic measurement of wall thickness was performed on two cast parts. The first cast part was made from cast steel and the second one from gray iron. The properties of materials from which the cast parts were made are described. Also the specifications of equipment which was used in ultrasonic measuring is described along with the description of the measuring process. In the end, the results of the measurings were analyzed, and the final conclusion was given.