Time series data could be incomplete due to a variety of reasons such as the errors in communications and sensor devices. This paper aims to restore the incomplete time-series medical data using the denoising diffusion probabilistic model (DDPM). A DDPM is applied to restore the missing values based on the model trained using the original data without loss. The proposed diffusion model-based signal restoration approach was successful in restoring the incomplete electrocardiogram signals up to 50%.