We present five spectra of the quasar HS1603+3820 (zem=2.542) taken over intervals of 0.2-1.6 years (0.7-5.4 months in the quasar rest frame) with the High Dispersion Spectrograph on the Subaru telescope, for the purpose of studying its intrinsic narrow absorption lines (NALs). This quasar shows a rich complex of C IV NALs near the emission redshift (dN/dz ∼ 12). We perform time variability analysis as well as covering factor analysis to separate intrinsic NALs, which are physically related to the quasar, from intervening NALs in 8 C IV systems. Only one of them, at zabs ∼ 2.43, shows both partial coverage and large variation in line strength, width, and position. Assuming that a change in the ionization state of the absorber causes the variability, a lower limit can be placed on the electron density (ne > 3.2 × 104 cm-3) and an upper limit on the distance from the continuum source (r < 6 kpc). On the other hand, if motion of clumpy gas causes the variability, the crossing velocity and the distance from the continuum source are estimated to be νcross > 8,000 km s-1 and r < 3 pc, assuming that the observed shift velocity does not exceed the escape velocity at that radius. If we adopt the dynamical model of Murray et al. (1995), we can obtain a much more strict constraint on the radius of the gas parcel, r < 0.2 pc. We are planning to monitor this quasar for several years so as to use intrinsic absorber's behavior as a direct check of wind models.