The validity of Horio's scaling law for bubbling fluidized beds was examined experimentally by using two geometrically similar fluidized beds (internal diameter, 57 mm and 230 mm). Pressure fluctuations at the plenum and bottom section of the fluidized beds, eruption bubble size and frequency were measured, and the power spectral density and standard deviation of pressure fluctuation were examined over a wide range of superficial gas velocity and bed height adjusted to satisfy the scaling law. The validity of the scaling law for bubbling fluidized beds was discussed by use of a model based on pressure fluctuation and bubble behavior between two geometrically similar fluidized beds.