To provide an external vibrator which can be fixedly inserted into a clearance between a concrete form and a timbering material while preventing vibration transmission efficiency from being adversely affected as much as possible, even if the width of the clearance is different.

The external vibrator includes an insertion part 3 which is inserted into a clearance between a concrete form and a timbering material in a part of a body 1 mounted with a vibration generating source 2. The insertion part 3 is configured by detachably mounting an adjustment plate 5 to a mounting base 4 on the side of the body 1, the mounting base 4 and the adjustment plate 5 include thick sections 41, 51 and thin sections 42, 52, respectively, and the thickness of the insertion part 3 can be adjusted by changing a mounting state of the adjustment plate 5 to the mounting base 4.