A stretchable sensing device includes at least one first unit structure, at least one second unit structure and a stretchable material layer. The first unit structure includes a first substrate and a first sensing element layer, wherein the first substrate includes multiple first slits and multiple first distribution regions defined by the first slits. The first sensing element layer includes multiple first sensing electrodes being electrically isolated to each other and located on the first substrate. The second unit structure is located on the first unit structure and includes a second substrate and a second sensing element layer located on the second substrate. The stretchable material layer is located between the first unit structure and the second unit structure, and provides a changeable spacing between at least two of the first sensing electrodes located on adjacent first distribution regions. A sensing method of the stretchable sensing device is also provided.