The present invention relates to a detergent composition containing (a) 2 to 30% by weight of an inorganic alkali, (b) 0.5 to 20% by weight of at least one surfactant selected from an anionic surfactant and a nonionic surfactant, (c) 0.01 to 2% by weight (based on calcium ion) of a calcium salt, (d) 0.1 to 15% by weight of a calcium ion-sequestering agent, (e) 1 to 30% by weight of a water-soluble organic solvent and (f) 20 to 95% by weight of water.