To provide a liquid diluting apparatus capable of obtaining a higher dilution ratio compared to the conventional one.

A plurality of flow passage 14 for dilution liquid is formed in a 1st body 10 and a communicating passage 20 for introducing a special liquid is connected to one flow passage 14 for dilution liquid in a plurality of the flow passage for dilution liquid. A cylindrical dial 26 covering an opening part of the communicating passage 20 is provided outside the 1st body 10 and a jet 30 penetrating from inside to outside is formed in the cylindrical dial 26. A liquid supply passage 46 is provided in a position across the cylindrical dial 26 to face the communicating passage 20, and the communication passage 20 is connected to the liquid supply passage 46 with the jet 30 to introduce the special liquid from the liquid supply passage 46 to the one flow passage 14 for dilution liquid. As a result, the dilution rate is increased compared to the conventional one having only one flow passage for dilution liquid because the special liquid is introduced into one flow passage for dilution liquid in a plurality of the flow passage 14 for dilution liquid without introducing the special liquid into another flow passage 14 for dilution liquid.