Provided is a compound or a pharmaceutically acceptable salt thereof which inhibits the activity of PI3K to regulate many biological processes including the growth, differentiation, survival, proliferation, migration, metabolism, and the like of cells and is therefore useful for the prophylaxis/therapy of diseases including inflammatory diseases, arteriosclerosis, vascular/circulatory diseases, cancer/tumors, immune system diseases, cell proliferative diseases, infectious diseases, and the like. The above problem was solved by providing a urea derivative shown in the present specification, or a pharmaceutically acceptable salt thereof.