To realize a method for identifying a vibration of a slab, capable of shortening a time taken for identifying a vibration mode of the slab, and to realize a vibration suppressing device, a method for arranging the vibration suppressing device, a construction floor structure and a vibration measuring apparatus.

First, acceleration sensors are installed on measurement positions P1-P4 set on a floor slab 16, and a vibration is applied by hammering the vicinity of each acceleration sensor by using an impact hammer 80. An acceleration detected by the acceleration sensor is displayed as a vibration spectrum by a vibration mode instrument 60. Next, the vibration mode is identified from the obtained vibration spectrum. In the case of measuring the slab of 6 m 10 m, a conventional method using a random vibrating machine takes about 4-5 hours for the measurement at a mesh of 500 mm, since measuring operations are carried out at 273 (=1321) points, whereas this method only takes about 30-40 minutes, since the vibration mode is measured by using four measurement positions. Therefore, the time for identifying the vibration mode can be shortened by using this method.