We systematically investigate the mid-infrared (MIR; {lambda}>3{mu}m) time variability of uniformly selected ~800 massive young stellar objects (MYSOs) from the Red Midcourse Space Experiment Source survey. Out of the 806 sources, we obtain reliable 9yr long MIR magnitude variability data of 331 sources at the 3.4{mu}m (W1) and 4.6{mu}m (W2) bands by cross-matching the MYSO positions with ALLWISE and NEOWISE catalogs. After applying the variability selections using ALLWISE data, we identify five MIR-variable candidates. The light curves show various classes, with the periodic, plateau-like, and dipper features. Out of the obtained two color-magnitude diagram of W1 and W1-W2, one shows "bluer when brighter and redder when fainter" trends in variability, suggesting change in extinction or accretion rate. Finally, our results show that G335.9960-00.8532 has a periodic light curve, with an ~690d cycle. Spectral energy density model fitting results indicate that G335.9960-00.8532 is a relatively evolved MYSO; thus, we may be witnessing the very early stages of a hyper- or ultra-compact HII region, a key source for understanding MYSO evolution.