A negative first group G.sub.1 is fixed when a power of the projection zoom lens varies and has a focusing function. A positive second group G.sub.2, a positive or negative third group G.sub.3, a positive fourth group G.sub.4 and a positive or negative group G.sub.5 move with a mutual relationship. A sixth group G.sub.6 functions as a relay lens. The fifth group G.sub.5 includes a cemented lens formed by cementing a negative meniscus lens L.sub.10 having a convex surface directed to the magnification side, a negative lens L.sub.11 and a positive lens L.sub.12 in order from a magnification side, and a positive lens L.sub.13 having a convex surface directed to a reduction side. Also, an expression |F5|/F>4.5 is satisfied where F denotes a focal length of the projection zoom lens at a wide-angle end and F5 denotes a focal length of the fifth group.