A digital map display zooming method for enlarging and reducing a displayed portion of a digital map as map information in digital form within a display screen, said method comprising the steps of: designating enlarging operation and reducing operation of said displayed portion of said digital map within said display screen with a pointing means (6, 12, 31, 32); and carrying out processing for performing enlarging operation and reducing operation of a displayed portion designated by said pointing means (6, 12, 31, 32), wherein said pointing means (6, 12, 31, 32) comprises a first designating part (6b, 31) and a second designating part (6c, 32), and the enlarging operation and the reducing operation of said displayed portion of said digital map are carried out by operating said first designating part (6b, 31) and said second designating part (6c, 32), respectively, wherein the method further comprises the steps of: storing a plurality of image data layers having different scale ratios; and performing the enlarging operation and the reducing operation of the displayed portion based on a certain image data layer of the plurality of image data layers, wherein the enlarging operation and the reducing operation of the displayed portion are performed based on another image data layer when the scale ratio (Snew) of the displayed portion becomes smaller than the scale ratio of the certain image data layer (Sn+1) or when the scale ratio (Snew) of the displayed portion becomes larger than a scale ratio (Sn-1) of another image data layer, and wherein the pointing means is a computer mouse and said first designating part is a left mouse button and said second designating part is a right mouse button or wherein said first designating part is a first touch pad and said second designating part is a second touch pad. designating enlarging operation and reducing operation of said displayed portion of said digital map within said display screen with a pointing means (6, 12, 31, 32); and carrying out processing for performing enlarging operation and reducing operation of a displayed portion designated by said pointing means (6, 12, 31, 32), wherein said pointing means (6, 12, 31, 32) comprises a first designating part (6b, 31) and a second designating part (6c, 32), and the enlarging operation and the reducing operation of said displayed portion of said digital map are carried out by operating said first designating part (6b, 31) and said second designating part (6c, 32), respectively, wherein the method further comprises the steps of: storing a plurality of image data layers having different scale ratios; and performing the enlarging operation and the reducing operation of the displayed portion based on a certain image data layer of the plurality of image data layers, wherein the enlarging operation and the reducing operation of the displayed portion are performed based on another image data layer when the scale ratio (Snew) of the displayed portion becomes smaller than the scale ratio of the certain image data layer (Sn+1) or when the scale ratio (Snew) of the displayed portion becomes larger than a scale ratio (Sn-1) of another image data layer, and wherein the pointing means is a computer mouse and said first designating part is a left mouse button and said second designating part is a right mouse button or wherein said first designating part is a first touch pad and said second designating part is a second touch pad. storing a plurality of image data layers having different scale ratios; and performing the enlarging operation and the reducing operation of the displayed portion based on a certain image data layer of the plurality of image data layers, wherein the enlarging operation and the reducing operation of the displayed portion are performed based on another image data layer when the scale ratio (Snew) of the displayed portion becomes smaller than the scale ratio of the certain image data layer (Sn+1) or when the scale ratio (Snew) of the displayed portion becomes larger than a scale ratio (Sn-1) of another image data layer, and wherein the pointing means is a computer mouse and said first designating part is a left mouse button and said second designating part is a right mouse button or wherein said first designating part is a first touch pad and said second designating part is a second touch pad.