To provide an ammonia diluting apparatus capable of enhancing the dissolving capacity of introduced ammonia gas and capable of suppressing the generation of noise and vibration during operation.

In the ammonia diluting apparatus which is equipped with a dilution tank 2 storing a diluent liquid and an introducing pipe 4 for introducing ammonia gas into the dilution tank 2 and dissolves the introduced ammonia gas in the diluent liquid, a fluid dispersing member for dispersing a flow of the ammonia gas is housed in the leading end part 20 of the introducing pipe 4 and an ammonia gas jet orifice 24 is formed at the position facing to the fluid dispersing member of the introducing pipe 4.