A layered lithium-nickel-based compound oxide powder for a positive electrode material for a high density lithium secondary cell, capable of providing a lithium secondary cell having a high capacity and excellent in the rate characteristics also, is provided.A layered lithium-nickel-based compound oxide powder for a positive electrode material for a lithium secondary cell, characterized in that the bulk density is at least 2.0 g/cc, the average primary particle size B is from 0.1 to 1 μm, the median diameter A of the secondary particles is from 9 to 20 μm, and the ratio A/B of the median diameter A of the secondary particles to the average primary particle size B, is within a range of from 10 to 200. In production of a layered lithium-nickel-based compound oxide powder, which comprises spray drying a slurry having a nickel compound and a transition metal element compound capable of substituting lithium other than nickel, dispersed in a liquid medium, followed by mixing with a lithium compound, and firing the mixture, the spray drying is carried out under conditions of 0.4≦G/S≦4 and G/S≦0.0012V, when the slurry viscosity at the time of the spray drying is represented by V (cp), the slurry supply amount is represented by S (g/min) and the gas supply amount is represented by G (L/min).