A tissue-piercing device includes two piercing members, and an operation section to which a proximal end of each of the piercing members is connected. Each of the piercing members includes a flexible outer sheath, a slidable inner sheath which is slidably inserted in the outer sheath, and a slidable needle which is inserted in the inner sheath. A switch portion is provided for switching between an operation mode in which a piercing action by the two piercing members is performed in a single operation, and an operation mode in which piercing actions by the two piercing members are performed in respective separate operations. The switch portion includes a sheath-coupling member to couple and decouple the two slidable inner sheaths. The switch portion may include a needle-coupling member to couple and decouple the two slidable needles.