In this study, the heat transfer problem for long-pulse laser treatment is evaluated semi-analytically. First, the derivation of the theoretical solution is presented. Subsequently, the validity of the semi-analytical solution is evaluated by comparing it to the numerical results obtained by the Pennes equation. The maximum temperature generated inside the tissue is evaluated as a function of laser power frequency and the cooling heat flux at the tissue surface. For low values of the angular frequency or high values of the cooling heat flux at the surface, the maximum temperature region is effectively located in a deeper region of the tissue. In addition, when the time scale of the variation of the laser power approaches the thermal conduction scale, the amplitude of the location of maximum temperature shows a linear correlation with the scale derived from the Fourier number. Finally, it is confirmed that control of the depth and the region of heating can be achieved when the angular frequency of the power variation of laser and/or the cooling heat flux at the surface is adjusted appropriately.