  Analyzing Chandra data of Tycho's supernova remnant (SNR) taken in 2000,
2003, 2007, 2009, and 2015, we search for time variable features of synchrotron
X-rays in the southwestern part of the SNR, where stripe structures of hard
X-ray emission were previous found. By comparing X-ray images obtained at each
epoch, we discover a knot-like structure in the northernmost part of the stripe
region became brighter particularly in 2015. We also find a bright filamentary
structure gradually became fainter and narrower as it moved outward. Our
spectral analysis reveal that not only the nonthermal X-ray flux but also the
photon indices of the knot-like structure change from year to year. During the
period from 2000 to 2015, the small knot shows brightening of $\sim 70\%$ and
hardening of $\Delta \Gamma \sim 0.45$. The time variability can be explained
if the magnetic field is amplified to $\sim 100~\mathrm{\mu G}$ and/or if
magnetic turbulence significantly changes with time.
