PURPOSE: To easily vary interior echo characteristics at low cost by constituting a device which adjusts the interior echo characteristics by adjusting the sound absorptivity of a wall surface or ceiling by arranging columnar members, which have parts differing in sound absorptivity in the external surfaces and can rotate in peripheral directions, in parallel.

CONSTITUTION: The echo adjusting device 1 is constituted by arranging plural triangle poles 2 in parallel, a shaft 3 penetrates in the axis of each triangle pole 2, and they are united in the rotary axis direction. Further, the lower end part of the shaft 3 is supported rotatably on an unshown bearing, a pinion gear 3a is provided at the upper end, and this gear is engaged with the rack gear 4a of a rack shaft 4 which is supported movably. Element materials such as felt materials which differ in sound absorptivity, i.e. echo characteristics, e.g. thickness are stuck on the external surfaces 2a and 2c of each triangle pole 2 and they are set in the same direction at all times. After operates a driving device to move back the rack shaft 4 and rotates the respective triangle pole 2 properly to form a surface which has optional sound absorptivity on the wall surface and ceiling.