A vehicle body side structure includes a flow redirecting member that introduces a traveling wind in a direction toward a wheel arch for a rear tire. The flow redirecting member has an inlet portion through which the traveling wind is introduced and an outlet portion through which air having been introduced through the inlet portion is ejected to the wheel arch side. The inlet portion is positioned in front of the wheel arch. The outlet portion has a slit shape extending along a surface of the rear tire on an outer side in a vehicle width direction.