Heat capacity of lithium nickel oxide of nearly stoichiometric composition (Li0.99Ni1.01O2) was measured using an adiabatic calorimeter between 13 and 300 K. Abnormally large heat capacity was observed below 20 K, and it seems be related to the spin glass transition observed in the magnetic susceptibility measurements of nearly stoichiometric samples of Li1-xNi1-xO2. The heat capacity value above 100 K was compared with LiCoO2 and it was found that the heat capacity of Li0.99Ni1.01O2 is much larger than that of LiCoO2 in spite of almost the same atomic weight, of Ni and Co. The heat capacity difference was discussed in terms of the lattice vibrations and bond strength in the crystals.