A substrate surface planarization method includes an arranging step of arranging a liquid curable composition onto a substrate surface having unevenness, a waiting step of waiting until the surface of the layer of the liquid curable composition becomes smooth, and a light exposure step of applying light to cure the layer of the liquid curable composition in this order. The arranging step includes a first arranging step of arranging a layer made of a first liquid curable composition (A1) containing at least a polymerizable compound (a1), and a second arranging step of arranging droplets of a second liquid curable composition (A2) containing at least a polymerizable compound (a2) onto the layer made of the first liquid curable composition (A1) by dropping the droplets discretely.