In an FOP 1, a glass body 8 is configured by including antimicrobial glass portions 10 made of antimicrobial glass containing Ag2O. Here, the glass containing silver does not have chemical durability, so that it has properties to easily emit Ag ions due to moisture. Ag ions have an excellent antimicrobial effect. Therefore, by configuring the glass body 8 to include the antimicrobial glass portions 10 containing Ag2O, the glass body 8 can obtain a sterilization effect due to the action of Ag ions. Therefore, the FOP 1 can be provided with antimicrobial activities.