PURPOSE: To provide a manual ultrasonic defect detector for detecting the defect positively without requiring skill.

CONSTITUTION: Rotary wheels 4 are arranged at four lower ends of a supporting machine body 1 provided with a handle 2. The rotational amount of one rotary wheel 4 is introduced through a belt 6 to a rotary encoder 7 which delivers a drive pulse to a pulse motor 9. A rolling ball screw shaft 11 interlocked with the pulse motor 9 is stretched across the supporting machine body 1 and a mechanism 13 supporting a probe 12, protruding at the lower end thereof, is screwed to the rolling ball screw shaft 11. This constitution realizes a correct scanning feed of the probe 12 at a predetermined speed depending on the rotational amount of the rotary wheel 4.