A dimming device, comprising: a pair of input terminals (11, 12) configured to be electrically connected between an illumination load and an AC power supply; a switching device (Ql, Q2; Q3) including a control terminal and configured to switch between non-conduction and conduction of a bidirectional current between the pair of input terminals (11, 12) depending on whether or not a voltage applied to the control terminal is higher than or equal to a threshold voltage (Vthl); an inputter configured to receive a dimming level specifying a magnitude of a light output of the illumination load; a signal source configured to generate a drive signal (Sdl) for the switching device (Q1, Q2, Q3) according to the dimming level; characterized by a discharge part including a series circuit having a Zener diode and a rectifier element connected in series to each other, the series circuit enabling passage of a reverse current of the Zener diode, and the series circuit being electrically connected between the control terminal and the signal source to enable the reverse current to flow from the control terminal to the signal source when the drive signal (Sdl) transitions from a High level to a Low level, the dimming device further comprising an auxiliary switch configured to switch between conduction and non-conduction between the control terminal and a reference potential point of the signal source, wherein a drain of the auxiliary switch is connected to the control terminal, and a source of the auxiliary switch is connected to the reference potential point, and wherein the auxiliary switch is configured to be turned on with a delay of a definite time from a fall of the drive signal (Sdl). a pair of input terminals (11, 12) configured to be electrically connected between an illumination load and an AC power supply; a switching device (Ql, Q2; Q3) including a control terminal and configured to switch between non-conduction and conduction of a bidirectional current between the pair of input terminals (11, 12) depending on whether or not a voltage applied to the control terminal is higher than or equal to a threshold voltage (Vthl); an inputter configured to receive a dimming level specifying a magnitude of a light output of the illumination load; a signal source configured to generate a drive signal (Sdl) for the switching device (Q1, Q2, Q3) according to the dimming level; characterized by a discharge part including a series circuit having a Zener diode and a rectifier element connected in series to each other, the series circuit enabling passage of a reverse current of the Zener diode, and the series circuit being electrically connected between the control terminal and the signal source to enable the reverse current to flow from the control terminal to the signal source when the drive signal (Sdl) transitions from a High level to a Low level, the dimming device further comprising an auxiliary switch configured to switch between conduction and non-conduction between the control terminal and a reference potential point of the signal source, wherein a drain of the auxiliary switch is connected to the control terminal, and a source of the auxiliary switch is connected to the reference potential point, and wherein the auxiliary switch is configured to be turned on with a delay of a definite time from a fall of the drive signal (Sdl).