PID control is a common and an effective approach in process industries. However, it is important to determine suitable PID gains included in the PID controller because the control performance strongly depends on these PID gains. In this paper, a new design scheme of PID controllers without using the system model in computing PID gains. That is, PID gains can be derived by using only the operating (input/output) data. Concretely, the generalized output is newly derived from the PID control law, and the PID gains are computed so that the generalized output approaches to the system output. As a result, the suitable PID gains can be obtained, which the system output approaches to the reference model output. The behavior of the proposed scheme is examined by numerical simulation examples and application to an injection molding process.