A valve element opening/closing device may include a main body, an inflow pipe, an outflow pipe, a valve element, and a drive part for driving the valve element to open and close a flow passage. The drive part may include a linearly moving mechanism part for driving the valve element, which may include a rotary power transmission member, a linearly moving member for moving the valve element, a turning prevention mechanism, and an urging member for urging the valve element in a closing direction. The turning prevention mechanism may include a shaft turnably supporting the rotary power transmission member, and a shaft hole formed in the linearly moving member that is supported by the shaft, and the shaft is engaged with the shaft hole to prevent turning of the linearly moving member.