A protective layer setting unit includes a protective agent and an application unit configured to apply the protective agent to an image carrying member in a manner sufficient to satisfy equations (1) and (2). A surface condition of the image carrying member is determined by an applied-agent amount index "X" and an agent coating ratio "Y," and a ratio of "X/Y" is set to 0.020 or less after applying the protective agent for 120 minutes. applied-agent amount index X=Sb/Sa (1) agent coating ratio Y=(A.sub.0-A)/A.sub.0.times.100(%) (2).