The microcanonical transfer matrix is used to study the distribution of Yang-Lee zeros of the Q-state Potts model in the complex magnetic-field (x=e^β h) plane for the first time. Finite size scaling suggests that at (and below) the critical temperature the zeros lie close to, but not on, the unit circle with the two exceptions of the critical point x=1 (h=0) itself and the zeros in the limit T=0.