This paper studies the third problem for the Laplace equation on a bounded planar domain with inside cracks. The third condition ∂u/∂n+hu=f is given on the boundary of the domain. The skip of the function u+−u−=g and the modified skip of the normal derivatives (∂u/∂n)+−(∂u/∂n)−+hu+=f are given on cracks. The solution is looked for in the form of the sum of a modified single-layer potential and a double-layer potential. The solution of the corresponding integral equation is constructed.