Provided is a plug device which includes: a body portion; and a valve element portion. A fluid flow passage is formed in the body portion. The fluid flow passage extends along an axis, and has a valve hole at one end thereof. The valve element portion is accommodated in the body portion in an advancing and retracting manner along the axis. A proximal end portion of the valve element portion is made of a conductive fluororesin material containing a fluororesin material and carbon nanotubes dispersed in the fluororesin material. The proximal end portion is conductive with a conductive member maintained at a ground potential. A volume resistivity of the conductive fluororesin material falls within a range of larger than 1.0x×103 Ω·cm and less than 1.0×104 Ω·cm.