The gas dissolution process of a spherical rising gas bubble was investigated experimentally and numerically. We developed an experimental system that uses a charged-coupled device (CCD) camera coupled with a microscope to follow the rising bubble. By measuring the bubble size and the rising speed from the bubble motion data captured by a personal computer, we could precisely estimate the drag coefficients and the Sherwood number for the dissolution of gas bubbles at Reynolds numbers below 100. We also numerically estimated the drag coefficients and Sherwood number for dissolution of gas bubbles in an infinite liquid by directly solving the Navier-Stokes equation and the convection-diffusion equation. The experimental and numerical results are in good agreement. Moreover, we compared the experimental results with several proposed equations for estimating the drag coefficients and Sherwood number and clarified the applicable region of each equation. Finally, based on correlation with the numerical results, we present an equation for estimating the Sherwood number in the range where the Reynolds number is less than 100 and the Peclet number is greater than 1.