Photoacoustic microscopy (PAM) is able to represent the light energy absorption of specific biological molecules (hemoglobin, melanin, DNA/RNA, lipid etc.) without the contrast agents. Especially, AR-PAM can overcome the optical diffusion limit and achieve much greater penetration depth up to a quasi-diffusive regime with low acoustic scattering. Therefore, AR-PAM has been significantly investigated in various applications for morphological, physiological, and molecular information. However, previously developed AR-PAM systems have limited field-of-view (FOV) and imaging speed. These barriers preclude AR-PAM systems from their application to exploratory preclinical and clinical trials. In this work, we introduce an ultra-wide-field AR-PAM system. We fabricated a water-proof microelectromechanical systems (MEMS) scanner for high-speed imaging integrated with two stepper-motors for wide-field scanning (30 × 80 mm2). Finally, we performed in-vivo experiments for preclinical and clinical applications to validate the developed AR-PAM system. For the preclinical experiment with mice, we visualized ventral, sagittal, and dorsal anatomical microstructures including vascular layers and inner organs non-invasively using one wavelength. An entire 3D volume data was acquired with the developed system and depth-encoded along the skin surface up to 2.3 mm. Subcutaneous multi-layers were differentiated on each layer according to distinct microstructures such as recognizable vasculatures and organs (mammary vessels, caudal vessels, popliteal vessels, intestine, heart, spline, etc.). Moreover, we have successfully obtained the distinct microstructures and microvascular networks of human fingers, palm and forearm in-vivo.