Interfacial adhesion is critical for short-fiber composites because their stiffness is significantly affected by the reduced load transfer capability at the fiber ends. If debonding progresses at the fiber ends under cyclic loading, it becomes a critical issue for material design. In this study, we investigate the debonding behavior at the fiber/matrix interface in short-fiber CFRP using finite element analysis (FEM). The analysis focuses on a single carbon fiber embedded in the matrix. The fiber-matrix domain is surrounded by an outer region with homogenized CFRP stiffness to represent far-field constraints. The finite element model used for this analysis is axisymmetric. Macroscopic strain is defined as the axial strain at the outer boundary. Cyclic loading is applied under strain control. The matrix is modeled as an elastoplastic material. The fiber/matrix interface was modeled using a cohesive zone model (CZM) with zero-thickness cohesive elements. The interfacial strength used in this model is derived from pin-hole pull-out tests. Frictional contact is active from the onset of loading, allowing cohesive tractions and tangential sliding resistance to coexist. For a representative baseline case, interfacial damage initiates at both fiber ends at a macroscopic strain of 0.7%, and the onset strain varies with interfacial strength and fracture toughness. At initiation, the shear stress　increases, indicating shear-dominated loading. Under strain-controlled cyclic loading, the deboned length increases with cycle number, demonstrating damage accumulation even at a fixed strain amplitude. After debonding, the interface becomes heterogeneous, separating into regions with frictional resistance only and regions where cohesive tractions coexist with frictional resistance. In summary, no debonding occurs under low-load conditions, whereas debonding initiates under high-load conditions and progresses with each cycle under repeated loading. Clarifying the relationship between macroscopic strain and debonding behavior is expected to support interface and material design for short-fiber composites.