A blood analyzer comprising: a sample preparing part configured to prepare a measurement sample from a blood sample, a staining dye to stain a nucleic acid, and diluent to contract red blood cells; a detecting part configured to detect the fluorescent light intensity and the scattered light intensity given off from the measurement sample irradiated with light; an output part; and an analyzing part configured to identify the population including red blood cells infected by ring-form malaria parasite based on the fluorescent light intensity and the scattered light intensity, and output to the output part the information relating to infection of Plasmodium falciparum based on the scattered light intensity distribution of particles associated with the identified population that includes red blood cells infected by the ring-form malaria parasite, wherein the population including red blood cells infected by the ring-form malaria parasite is a population including the single ring-form malaria parasite, which is a third particle group in which the scattered light intensity is less than that of a first particle group of the population including white blood cells, and the fluorescent light intensity is less than that of the first particle group and greater than that of a second particle group of the population including red blood cells not infected by malaria parasite, wherein the analyzing part is configured to output to the output part the information relating to infection of Plasmodium falciparum based on a representative value of the scattered light intensity of particles belonging to the third particle group, and wherein the analyzing part is configured to output to the output part information indicating a possibility of infection of the blood sample by Plasmodium falciparum on the basis that the representative value is less than a predetermined numerical value for discrimination between Plasmodium falciparum and other species of malaria parasite. a sample preparing part configured to prepare a measurement sample from a blood sample, a staining dye to stain a nucleic acid, and diluent to contract red blood cells; a detecting part configured to detect the fluorescent light intensity and the scattered light intensity given off from the measurement sample irradiated with light; an output part; and an analyzing part configured to identify the population including red blood cells infected by ring-form malaria parasite based on the fluorescent light intensity and the scattered light intensity, and output to the output part the information relating to infection of Plasmodium falciparum based on the scattered light intensity distribution of particles associated with the identified population that includes red blood cells infected by the ring-form malaria parasite, wherein the population including red blood cells infected by the ring-form malaria parasite is a population including the single ring-form malaria parasite, which is a third particle group in which the scattered light intensity is less than that of a first particle group of the population including white blood cells, and the fluorescent light intensity is less than that of the first particle group and greater than that of a second particle group of the population including red blood cells not infected by malaria parasite, wherein the analyzing part is configured to output to the output part the information relating to infection of Plasmodium falciparum based on a representative value of the scattered light intensity of particles belonging to the third particle group, and wherein the analyzing part is configured to output to the output part information indicating a possibility of infection of the blood sample by Plasmodium falciparum on the basis that the representative value is less than a predetermined numerical value for discrimination between Plasmodium falciparum and other species of malaria parasite.