Pathogenic bacteria of Mycoplasma pneumonia, Mycoplasma pneumoniae, do not respond to β-lactam antimicrobial agents. Therefore, it is clinically important to promptly identify infection with this type of bacteria. However, conventional examination methods such as culture and antibody tests are not useful for the rapid diagnosis of this bacterial type. In this study, we examined a Loopamp Mycoplasma P-detecting Reagent Kit developed based on the LAMP (Loop-mediated isothermal amplification) method, which may overcome the limitations of the conventional methods. The consistency rate for the conventional polymerase chain reaction (PCR) method was 98.3%. That for a rapid antibody test, immunocard Mycoplasma antibody, was 54.0%, suggesting the limitation of the rapid antibody test. We compared a pretreatment method using a Loopamp PURE DNA Extraction Kit, as a simple DNA extraction method, with that using a QIAamp DNA Mini Kit. The consistency rate was 91.4%, suggesting the usefulness of the simple DNA extraction method. The use of this kit may facilitate a more rapid diagnosis. The Loopamp Mycoplasma P-detecting Reagent Kit is useful for the accurate and rapid diagnosis of Mycoplasma pneumoniae infection.