A method for accurately counting desired cells or microorganisms (viable bacteria) in a sample fluid in which contaminants are included is provided. One or plural types of membrane-permeable fluorochromes whose fluorescence amount is amplified by binding to a nucleic acid and glycerin are added to a sample fluid containing cells or microorganisms to be counted and allowed to stand for a certain time. Glycerin is added before or after or simultaneously with the mixing of the sample fluid and the fluorochrome(s). The cells or microorganisms to be counted are counted by staining the cells or microorganisms to be counted, followed by irradiating with light having a specific wavelength to detect the fluorescence emitted from the cells or microorganisms.