The effect of oblique functional gradation to thermal stresses in the semi-infinite body is studied theoretically. The rigorous solution is derived by the use of the variable separation and the stress function method. The material properties are assumed to be exponential functions of the position along the functionally graded direction. Two types of boundary conditions are considered, one is the prescribed heat flux on the heating surface and the other is the prescribed temperature on the same surface. The numerical calculations are carried out for ZrO2 /Ti-6Al-4V functionally graded materials (FGMs). The numerical results of temperature and thermal stresses are illustrated with figures for different values of an oblique angle. Numerical results for the prescribed temperature boundary condition show that the temperature curve leans to the ceramic-rich side and the compressive stress decreases with increasing the oblique angle when the oblique angle varies from 0° to 45°.