A valve opening and closing mechanism includes: an input shaft 2 driven by a power source; two or more output shafts 5, 6 respectively including valves 3, 4; power transmission members that transmit power from the input shaft 2 to the respective output shafts 5, 6 with varying a phase of the power; and preload application members that apply preloads respectively to the output shafts 5, 6 and the power transmission member in opposite directions. The output shafts 5, 6 may be separated from the power transmission member.