A positive electrode active material for nonaqueous electrolyte secondary batteries contains a lithium transition metal composite oxide that contains not less than 80% by mole of Ni relative to the total number of moles of metal elements other than Li; and Ti is present at least in the surfaces of particles of the composite oxide. With respect to this positive electrode active material, if particles having a volume-based particle diameter more than the 70% particle diameter (D70) are taken as first particles and particles having a volume-based particle diameter less than the 30% particle diameter (D30) are taken as second particles, the molar fraction (A2) of Ti relative to the total number of moles of metal elements in the surfaces of the second particles is higher than the molar fraction (A1) of Ti relative to the total number of moles of metal elements in the surfaces of the first particles.