A new method to evaluate the mode I stress intensity factor for a semi-circular surface crack subjected to a three-dimensional complicated stress distribution under ball-on-plate contact loading was proposed. Fabrikant & Hanson's equation, which was originally derived to evaluate the stress intensity factor of a penny-shaped subsurface crack, was applied for this problem, and the obtained value was compared with the result of the three-dimensional finite element analysis. The ratio of them was almost constant irrespective of the applied load, the crack radius and the distance from the contact point to crack. Multiplying the ratio as the correction factor for a surface effect in the value obtained from the method using Fabrikant & Hanson' equation, the stress intensity factor for a semi-circular surface crack under ball-on-plate contact loading could be evaluated conveniently.