In an electronic watermark detecting/inserting device which includes an electronic watermark detecting section (30) for detecting a first electronic watermark from a first DCT coefficient of an input digital image to produce a request for insertion of a second electronic watermark and an electronic watermark inserting section (20) for producing, in response to the request for insertion of the second electronic watermark, an output digital image which includes the first electronic watermark inserted therein and the second electronic watermark inserted subsequently to the first electronic watermark in the output digital image and which has the second DCT coefficient, a second DCT coefficient producing section (40) produces the second DCT coefficient from the output digital image. A DCT coefficient supplying section (50) supplies the second DCT coefficient from the second DCT coefficient producing section to the electronic watermark detecting section. The electronic watermark detecting section detectes, when supplied with the second DCT coefficient from the DCT coefficient supplying section, the second electronic watermark from the second DCT coefficient and produces a detection result representative of a detection intensity of the second electronic watermark to deliver the detection result to the electronic watermark inserting section. The electronic watermark inserting section adjusts, in response to the detection intensity represented by the detection result, an insertion intensity of the second electronic watermark to be inserted into the input digital image.