Abstract: A sound effect adjusting device includes: an effect pedal; a pedal board including a first housing, a three-way toggle switch, a microswitch, and a mounting member; the first housing including an input interface, an output interface, a send interface and a return interface formed thereon; the three-way toggle switch having a first contact blade electrically connected with the input interface, a second contact blade electrically connected with the send interface, a third contact blade electrically connected with the microswitch; the mounting member having a first pins assembly electrically coupled to the effect pedal; while the effect pedal assembled with the pedal board, the microswitch is off, and operates the three-way toggle switch so that the effect pedal is connected between the input interface and the output interface in series, or, the effect pedal connected between the send interface and the return interface in series.