A bacteria analyzing method comprising: irradiating with light a measurement sample prepared by mixing a specimen and a reagent; obtaining two types of optical information from each of at least some particles contained in the measurement sample as measurement data, the two types of optical information being forward scattered light intensity and fluorescence intensity; and generating a flag representing a morphologic type of bacteria contained in the specimen, the flag being indicative of bacillus, coccus or mix of bacillus and coccus; characterized in that the flag is generated by: creating a scattergram data table (Ts) holding the frequency of measurement data at each coordinate position on a coordinate system having a horizontal axis representing fluorescence intensity and a vertical axis representing forward scattered light intensity; creating a histogram data table (Th) holding frequency data (Fk) regarding the frequency of appearance of particles contained in each of a plurality of angle regions (θk) in the coordinate system; obtaining angle information of an angle region having the maximum frequency data in the histogram data table as declination information (θp); calculating a proportion (α) of the frequency in a low angle region (θL) relative to the frequency in the entire angle region (θ1... θm), the low angle region (θL) being an angle region included in the range of 0° to a angle θa preset between 0° < θa < 30°; generating (S109, S110, S111) a flag indicative of bacillus when the declination information (θp) is less than or equal to a threshold angle (θs) and when the proportion (α) is greater than or equal to a threshold value (αs); generating (S109, S110, S112) a flag indicative of a mix of bacillus and coccus when the declination information (θp) is less than or equal to the threshold angle (θs) and when the proportion (α) is less than the threshold value (αs); and generating (S109, S113) a flag indicative of coccus when the declination information (θp) exceeds the threshold angle (θs). irradiating with light a measurement sample prepared by mixing a specimen and a reagent; obtaining two types of optical information from each of at least some particles contained in the measurement sample as measurement data, the two types of optical information being forward scattered light intensity and fluorescence intensity; and generating a flag representing a morphologic type of bacteria contained in the specimen, the flag being indicative of bacillus, coccus or mix of bacillus and coccus; characterized in that the flag is generated by: creating a scattergram data table (Ts) holding the frequency of measurement data at each coordinate position on a coordinate system having a horizontal axis representing fluorescence intensity and a vertical axis representing forward scattered light intensity; creating a histogram data table (Th) holding frequency data (Fk) regarding the frequency of appearance of particles contained in each of a plurality of angle regions (θk) in the coordinate system; obtaining angle information of an angle region having the maximum frequency data in the histogram data table as declination information (θp); calculating a proportion (α) of the frequency in a low angle region (θL) relative to the frequency in the entire angle region (θ1... θm), the low angle region (θL) being an angle region included in the range of 0° to a angle θa preset between 0° < θa < 30°; generating (S109, S110, S111) a flag indicative of bacillus when the declination information (θp) is less than or equal to a threshold angle (θs) and when the proportion (α) is greater than or equal to a threshold value (αs); generating (S109, S110, S112) a flag indicative of a mix of bacillus and coccus when the declination information (θp) is less than or equal to the threshold angle (θs) and when the proportion (α) is less than the threshold value (αs); and generating (S109, S113) a flag indicative of coccus when the declination information (θp) exceeds the threshold angle (θs). creating a scattergram data table (Ts) holding the frequency of measurement data at each coordinate position on a coordinate system having a horizontal axis representing fluorescence intensity and a vertical axis representing forward scattered light intensity; creating a histogram data table (Th) holding frequency data (Fk) regarding the frequency of appearance of particles contained in each of a plurality of angle regions (θk) in the coordinate system; obtaining angle information of an angle region having the maximum frequency data in the histogram data table as declination information (θp); calculating a proportion (α) of the frequency in a low angle region (θL) relative to the frequency in the entire angle region (θ1... θm), the low angle region (θL) being an angle region included in the range of 0° to a angle θa preset between 0° < θa < 30°; generating (S109, S110, S111) a flag indicative of bacillus when the declination information (θp) is less than or equal to a threshold angle (θs) and when the proportion (α) is greater than or equal to a threshold value (αs); generating (S109, S110, S112) a flag indicative of a mix of bacillus and coccus when the declination information (θp) is less than or equal to the threshold angle (θs) and when the proportion (α) is less than the threshold value (αs); and generating (S109, S113) a flag indicative of coccus when the declination information (θp) exceeds the threshold angle (θs).