A time-dependent thermal stress field in a semi-infinite plane having a semi-infinite crack parallel to the edge of the plate was analyzed when the vicinity of the crack tip was locally heated. The straight boundary of the semi-infinite plate were assumed to be kept at zero temperature or thermally insulated. The thermal stress field was analyzed after each stepwise time advance by the Body Force Method. It was found that a mixed mode deformation occurs at the crack tip independently of the heating time and the stress intensities of mode I and II vary with the heating location. Moreover, the increase of heat dissipation from the plate surfaces may be effective for the decrease of K_II
