The present invention relates to a method of diagnosing cancer and predicting cancer type using cell-free nucleic acid fragments and image analysis technology, and more particularly, to a method of diagnosing cancer and predicting cancer type by extracting nucleic acids from a biological sample to obtain sequence information (reads), aligning the obtained reads, generating an image including size and coverage information of nucleic acid fragments based on the aligned reads, and then analyzing values calculated by inputting the image into a trained artificial intelligence model. The method of diagnosing cancer and predicting cancer type using size and coverage information of cell-free nucleic acid fragments according to the present invention advantageously shows high sensitivity and accuracy because it generates vectorized data and performs analysis using an AI algorithm.