A functional liquid tank is adapted to receive functional liquid from a functional liquid supply source and to supply the functional liquid to an inkjet functional liquid droplet discharge head. The functional liquid tank includes a tank body, a liquid column pipe, upper and lower limit liquid level detection units, a float member, and a float-regulating member. The float member is accommodated within the tank body with a small gap formed between the float member and an inside wall of the tank body. The float-regulating member is configured and arranged to regulate a descending end position of the float member when the float member descends as a liquid level within the tank body descends.