Heat capacities of (Hf1-yAly)O-0.17 (y=0-0.03) were measured from 325 to 905 K by using an adiabatic scanning calorimeter. A heat capacity anomaly was observed around 700 K for all (Hf1-yAly)O-0.17 samples and assigned to an order-disorder rearrangement of oxygen atoms. The experimental transition temperatures, the enthalpy change and entropy changes due to the order-disorder transition decreased with increasing aluminium contents. The experimental entropy changes of the order-disorder transition are compared with the theoretical values from the view point of statistical thermodynamics and are discussed.