The present invention relates to a method for producing target protein in plant cell culture, more particularly to the method for producing target protein comprising the steps of i) constructing vector containing SWPA2 promoter and gene for the target protein, ii) introducing said vector into Agrobacterium, iii) transforming said Agrobacterium into plant cell, and iv) mass-producing target protein using said transformed plant cells. The method of the present invention can mass-produce target proteins such as human lactoferrin. Moreover, the transformed plant can also be used to make health foods when medicinal plant is used as a host cell.