The present invention provides a monitoring method and a monitoring device, belongs to the field of electronic monitoring technology, and can solve the problem that useless video data occupies storage space and key video cannot be extracted quickly when an event occurs in the existing monitoring device. The monitoring method of the present invention comprises: determining whether or not a first image is changed; generating a storage instruction if it is determined that the first image is changed; collecting and storing images of external environment according to the storage instruction; obtaining a second image according to the collected images of external environment; determining whether or not the second image is changed; and stopping storing images of external environment if it is determined that the second image is not changed.