A vehicle body side part structure having high strength against a load in a frontal collision and a load in a side collision. A side panel outer member (14) is provided with a front pillar lower section (31) which is formed from a high-tensile steel sheet, a front pillar upper section (37a) which is formed from a normal steel sheet, and a reinforcement member (38) which is disposed along the front pillar upper section. The upper end (31a) of the front pillar lower section (31) is joined to the inner surface of the lower end (37c) of the front pillar upper section. The front end (38a) of the reinforcement member (38) is joined to the inner surface of the upper end (31a) of the front pillar lower section.