  We report monitoring observations of the T Tauri star EX Lupi during its
outburst in 2008 in the CO fundamental band at 4.6-5.0 um. The observations
were carried out at the VLT and the Subaru Telescope at six epochs from April
to August 2008, covering the plateau of the outburst and the fading phase to a
quiescent state. The line flux of CO emission declines with the visual
brightness of the star and the continuum flux at 5 um, but composed of two
subcomponents that decay with different rates. The narrow line emission (50 km
s-1 in FWHM) is near the systemic velocity of EX Lupi. These emission lines
appear exclusively in v=1-0. The line widths translate to a characteristic
orbiting radius of 0.4 AU. The broad line component (FWZI ~ 150 km s-1) is
highly excited upto v<=6. The line flux of the component decreases faster than
the narrow line emission. Simple modeling of the line profiles implies that the
broad-line emitting gas is orbiting around the star at 0.04-0.4 AU. The
excitation state, the decay speed of the line flux, and the line profile,
indicate that the broad-line emission component is physically distinct from the
narrow-line emission component, and more tightly related to the outburst event.
