The present disclosure relates to a method and device for detecting concealed dangerous objects in microwave images. The method includes: simultaneously processes multiple adjacent microwave images, obtains edge images of a single image by using two methods for each image, obtains dangerous-object edges of the single image by edge fitting operation, obtains a rough dangerous-object contour by performing a registration operation and a second edge fitting operation on the dangerous-object edges of the multiple images, and performs a regional-binarization operation and a filtering on the rough dangerous-object contour to obtain a second dangerous-object area. The present disclosure has high detection accuracy and calculation efficiency.