An electrophotographic developer comprising at least one element selected from the group consisting of boron and phosphorus in a content of 0.1 to 100 ppm, which the developer is excellent in flowability and shelf stability, does not give image defects such as occurrence of white stripes and attains almost constant image quality even when the ambient conditions including temperature and humidity fluctuate. A production process of a polymerized toner used in the developer, a production process of the developer, and an image forming process.