It is shown that the resonance-like phenomena or the relaxation oscillations in the light output of the directly modulated injection lasers is suppressed by a non-resonant π-type electric circuit connected to the laser diode. Application of this suppressor circuit is not sensitive to the bias current of laser diode and the cut-off frequency of modulation is sufficiently large. It is pointed out that the use of this method at the narrow stripe laser is the most effective.