To provide a vibration-detecting unit, which can be reduced in cost and size and which always detects the vibration component in the vertical direction, even if the holding direction is changed.

A pair of first rotary units 7 which are conductive and oppositely mounting a rotary shaft (b) provided on a first assembly board, having a vibration sensor for mainly detecting the vibration of the vertical direction from the rotary shaft (b) as a main vibration component, while similarly detecting the vibration of the shaft (b) are coupled rotatably with a pair of second rotary units 26 which is conductive and oppositely mounting a rotary shaft (b) provided on a second assembly board, while similarly detecting the vibration of the shaft (b). The center of the gravity of the first assembly board is disposed out of the shaft (b) in the vertical direction for detecting the vibration by the vibration sensor 6. The vibration in the vertical direction can always be detected with a single-vibration sensor, without occupying the rotary space by a large amount with the vibration as the main vibration component.