We describe the construction and performance of a scintillating fiber detector used in the near detector for the K2K (KEK to Kamioka, KEK E362) long baseline neutrino oscillation experiment. The detector uses 3.7 m long and 0.692 mm diameter scintillating fiber coupled to image-intensifier tubes (IIT), and a CCD camera readout system. Fiber sheet production and detector construction began in 1997, and the detector was commissioned in March, 1999. Results from the first K2K runs confirm good initial performance : position resolution is estimated to be about 0.8 mm, and track finding efficiency is $98 \pm 2$ % for long tracks (i.e., those which intersect more than 5 fiber planes). The hit efficiency was estimated to be $92 \pm 2$ % using cosmic-ray muons, after noise reduction at the offline stage. The possibility of using the detector for particle identification is also discussed.