A path in an edge-colored graph is called a rainbow path if every two distinct edges of the path have different colors. A graph whose every pair of vertices are linked by a rainbow path is called a rainbow-connected graph. The rainbow connection number of a graph is the minimum number of colors that are needed to color the edges of the graph such that the graph is rainbow-connected. In this paper, we determine the rainbow connection number of the commuting graph of a finite nonabelian group, which is a graph whose vertex set is a nonabelian group of finite order and two distinct elements of the group is adjacent in the graph if they commute. We also show that the rainbow connection number of the commuting graph of a finite group is related to the number of maximal abelian subgroups or the number of involutions that do not commute with any other nonidentity element of the group.