A polishing composition that can suppress surface defects and reduce haze is provided. A polishing composition includes: abrasives; at least one water-soluble polymer selected from vinyl alcohol-based resins having a 1,2-diol structural unit; and an alkali compound, where an average particle size of particles in the polishing composition measured by dynamic light scattering is not more than 55 nm. Preferably, the polishing composition further includes a non-ionic surfactant. Preferably, the polishing composition further includes a polyalcohol.