An object of the present invention is to provide better formulations of a latanoprost ophthalmic solution. The present invention provides a clear ophthalmic solution comprising latanoprost as an active ingredient and benzalkonium chloride as a preservative wherein white turbidity due to a change of formulation is prevented by at least one means selected from the following 1) to 3)； 1) adding a surfactant, 2) using benzalkonium chloride represented by the formula of [C6H5CH2N(CH3)2R]Cl (wherein R is alkyl having 12 carbon atoms) as the preservative and 3) adding a nonionic tonicity agent as a tonicity agent.
