Shape from focus (SFF) is a 3D shape measurement technique using a monocular camera. SFF also provides an all-in-focus image from multiple defocus images. In SFF, the pixelwise focused camera position and pixel data are determined from the degree of focus (focus measure). We previously reported that the optimal window size in the focus measure computation for accurate 3D shape measurement depends on the local texture frequency of objects. In this study, we validate the performance of the all-in-focus image reconstruction. We performed two tests: image quality validation using human tissue slides and a feasibility test using animal tissue. First, the image quality was validated using the similarity between reference images and reconstructed images of five human tissue slides. Second, the surface texture of an animal tissue was reconstructed as a feasibility test. The experimental results show that the similarity of the reconstructed images was significantly high, and the precise texture of the tissue 3D surface could be clearly observed. From the experiments, we demonstrate the reconstruction performance of the all-in-focus image by SFF both quantitatively and qualitatively.