A flame detecting method and device are provided to improve the accuracy of flame detection and reduce the possibilities of the false fire alarm. The flame detecting method and device capture a plurality of images of a monitored area; determines whether a moving area image exists in the plurality of images; analyzes at least one of a color model and a flickering frequency of the moving area image to generate a first analyzed result and compares the first analyzed result with a feature of a reference flame image; analyzes at least one of a variation of a location and an area of the moving area image to generate a second analyzed result and compares the second analyzed result with a predetermined threshold; and determines whether the moving area image is a flame image based on results of the comparing steps.