12 Leads ECG is essential for examining cardio status. However, most commercial-grade products only measure the DII Lead signal. And so, Reconstructed 12 Leads ECG Signal might be a better solution for identifying arrhythmia for data collected by smart devices. Here I built a Deep Learning model with U-Net Architecture for this specific task. GitHub Link: https://github.com/hawkiyc/12_Leads_ECG_Reconstruction_wtih_U_Net