Provided are a method of manufacturing a flexible piezoelectric energy harvesting device using a piezoelectric composite, and a flexible piezoelectric energy harvesting device manufactured by the same. The method of manufacturing the flexible piezoelectric energy harvesting device includes: forming a first electrode layer on a first flexible substrate; spin-coating a piezoelectric composite layer on the first electrode layer, wherein the piezoelectric composite layer is produced by mixing piezoelectric powder with polymer; performing heat treatment on the piezoelectric composite layer to harden the piezoelectric composite layer; and bonding a second flexible substrate with a second electrode layer on the hardened piezoelectric composite layer. Therefore, it is possible to simplify a manufacturing process and manufacture a high-performance flexible piezoelectric energy harvesting device having various sizes and patterns.