A controller of a cantilever evaluation system calculates a stream function value ψz(x, y; t+1) and vorticity ωz(x, y; t+1) at a subsequent time step t+1 using boundary conditions according to displacement h(z; t) of a cantilever and velocity δh/δt(z; t), a stream function value φz(x, y; t) and vorticity ωz(x, y; t) in two-dimensional planes. The controller uses the calculated stream function value φz(x, y) and vorticity ωz(x, y) to calculate a fluid drag force acting on the cantilever. The controller substitutes the calculated fluid drag force into a displacement calculation equation to calculate the displacement h(z; t+1) of the one-dimensional beam at the subsequent time step t+1. The controller repeats such calculation for each grid point and further repeats it at each time step.