Periodicity behavior was observed after droplet collision in viscous solutions with controlled glycerol concentrations onto a PDMS surface. No periodic movement was observed in the droplets at glycerol concentrations of 50% or more. In contrast, the vertical diameter of the droplets increased and decreased periodically at glycerol solution concentrations of 40% or less. Moreover, there was little change in the periodicity of the impacting droplet movement, and the vibration frequency was measured at approximately 80 to 98 Hz in the entire range. The maximum droplet spreading factor after collision decreased significantly with increasing glycerol concentrations of 40% or more (Ohnesorge number 1.4 × 10^-2 or more). The results suggest that the effect of viscosity became greater than that of the solution surface tension with increasing glycerol concentrations.