Tone synthesis apparatus synthesizes a tone of a wind instrument generated in response to vibration of a reed contacting a lip during a performance of the wind instrument. First arithmetic operation section solves a motion equation (A1) representative of behavior of the reed in an equilibrium state with external force acting on the lip and a second motion equation (A2) representative of behavior of the lip in the equilibrium state, to thereby calculate displacement yb(x), y0(x) of the lip and reed in the equilibrium state. Second arithmetic operation section solves a motion equation of coupled vibration of the lip and reed with calculation results of the first arithmetic operation section used as initial values of the displacement yb(x), y0(x) of the lip and reed, to thereby calculate the displacement y(x, t) of the reed. Tone is synthesized on the basis of the displacement y(x, t) calculated by the second arithmetic operation section.