To provide a sand level detecting instrument for continuously detecting the level of fluidized sand in a fluidized bed apparatus used for heat treatment of wire rod, etc.

In the sand level detecting instrument 1 composed of a float and an indicating rod, the float is disposed in the fluidized bed and the indicating rod is formed as bar shape and connected with the float at the one and extended from the inner part of the fluidized bed to the outer part at the other end. The float is vertically shifted with the sand level, and since the indicating rod is vertically shifted introduced by an introducing hole passed through outside from the inner part of the fluidized bed, the sand level can be observed from the outer part by observing the indicating rod coming outside. The piling of sand on the upper part of the float is prevented by forming the upper part of the float as a cone shape. Alarm can be generated when the sand level becomes abnormal, by arranging an upper and lower limiter 4 of the sand level near the indicating part 1b at the outer part of the fludized bed.