To reduce an absolute value of a measuring error and to simply improve a measuring accuracy by attaching a bottom of a capacity rod with a scale having a smaller inner sectional area than that of a measuring container perpendicularly to a surface of a liquid, and calculating a capacity of the liquid according to the specific formula.

A bottom of a capacity rod 2 with a scale having a smaller inner sectional area S2 than that S1 of a measuring container 1 is attached perpendicularly to a surface of a liquid. A zero scale base line of the rod 2 is matched to a scale base line T0 directly under a predetermined meniscus liquid position 3 of the container 1. Then, a meniscus position 3 is measured with an eye by the scale of the rod 2 as ΔT2, and a liquid volume V (cm3) in the container 1 is calculated according to the formula V=V1+(S1-S2).ΔT2, wherein V1 is a liquid amount (cm3) of the base line T0, S1 is the inner sectional area (cm2) of the container 1, S2 is an inner sectional area of the rod 2, and ΔT2 is a designated scale value (cm) of the rod 2 indicating a liquid level from the line T0 to the position 3.