The objective of this study was to develop a simulation model for monofin swimming which considers the mechanical interaction between the monofin and swimmer. For this objective, the swimming human simulation model SWUM was extended to the monofin swimming. In order to identify the bending stiffness and damping coefficient of the monofin, the static and dynamic bending tests of a monofin were conducted. From the identification process, it was found that the simulation using the identified parameters reproduced the experiment well. This suggests the validity of the modeling of the monofin itself. The body geometry and joint motion of the swimmer were acquired from the experiment using a subject swimmer. In order to identify the fluid force coefficients of the monofin, the fluid force acting on the monofin was measured in the experiment which was conducted in a circulating water tank. The simulation with the identified parameters reproduced the experiment well. This suggests the validity of the fluid force model for the monofin. From the simulation of monofin swimming using the identified model parameters, it was found that the whole behavior of the swimmer and monofin in the simulation agrees well with that in the experiment, especially for the bending motion of the monofin. The velocities averaged in one kicking cycle in the simulation and experiment also agreed within a 10% error. These results sufficiently suggest the validity of the developed simulation model.