To determine the presence and resistance degree of a penicillin- resistant Streptococcus pneumoniae important to countermeasures for infectious diseases by simultaneously detecting an 1ytA gene, a pbpla gene and a pbp2b gene of the Streptococcus pneumoniae according to a gene amplification method.

A DNA corresponding to the 694th to the 966th positions of an 1ytA gene, a DNA corresponding to the 2256th to the 2685th positions of a pbpla gene and a DNA corresponding to the 1636th to the 1712nd positions of a pbp2b gene of Streptococcus pneumiae are simultaneously detected according to a gene amplification method by a polymerase amplification reactional method using a primer having base sequences represented by formulas I to VI. Thereby, a penicillin-resistant Streptococcus pneumoniae can directly and rapidly be detected from a specimen with a high accuracy and the presence and resistance degree of the penicillin-resistant Streptococcus pneumoniae can be determined for a patient suffering from an infectious disease caused by the Streptococcus pneumoniae to carry out proper prevention and treatment in an early stage.