This study aims to clarify the requirements for designing a canonical controller using data obtained from unknown systems. Based on Willems’ fundamental lemma, this study discusses the conditions under which the system’s data can achieve the desired behavior, and then clarifies the data requirements for a canonical controller. The clarified requirements provide sufficient conditions for designing a canonical controller using finite-length data. Furthermore, simulations were conducted to examine the practicality of the clarified requirements. The simulation results demonstrate that adding disturbances to the reference input can extend the finite interval that satisfies the design requirements for a canonical controller.