Provided is a fiber laser system including fiber containing dysprosium. The fiber laser system uses 1.7-.mu.m pump light. A resonator of the fiber laser system includes a dichroic mirror, a partial reflection mirror, and/or an FBG. Therefore, the fiber laser system can provide 3-.mu.m laser light and have high light pumping efficiency and high output power. The fiber laser system includes: fiber including dysprosium, a pump light source disposed at a side of the fiber and emitting pump light having a wavelength exciting electrons of the dysprosium from a ground energy level .sup.6H.sub.15/2 to an energy level .sup.6H.sub.11/2; a first reflection member, disposed between the fiber and the pump light source, transmitting the pump light, and reflecting first lasing light having a first wavelength; and a second reflection member, disposed at a side opposite to the pump light source with respect to the fiber, transmitting a portion of the first lasing light.