A sheet pressure sensor comprising: a first fiber layer that has a plurality of first conductive portions having conductivity, and a plurality of first non-conductive portions electrically insulating the plurality of first conductive portions, respectively; a second fiber layer that is disposed oppositely to the first fiber layer and distanced away from the first fiber layer, and has a second conductive portion having conductivity; a third fiber layer that is provided between the first fiber layer and the second fiber layer; and a measuring instrument for measuring electric resistance between the plurality of first conductive portions and the second conductive portion, wherein, the third fiber layer is configured of a plurality of connecting yarns that is extended from one of the plurality of first conductive portions and the second conductive portion to another thereof to connect the plurality of first conductive portions and the second conductive portion, characterized in that: the plurality of connecting yarns further electrically connects the plurality of first conductive portions and the second conductive portion with a predetermined electric resistivity, respectively, and, when the first fiber layer or the second fiber layer is deformed by pressure application, a connecting yarn near the pressure application among the plurality of connecting yarns deforms due to the first or second fiber layer deformation and shortens a length of a conducting path (L, L') formed by the connecting yarn between the plurality of first conductive portions and the second conductive portion to reduce electric resistance between the plurality of first conductive portions and the second conductive portion. a first fiber layer that has a plurality of first conductive portions having conductivity, and a plurality of first non-conductive portions electrically insulating the plurality of first conductive portions, respectively; a second fiber layer that is disposed oppositely to the first fiber layer and distanced away from the first fiber layer, and has a second conductive portion having conductivity; a third fiber layer that is provided between the first fiber layer and the second fiber layer; and a measuring instrument for measuring electric resistance between the plurality of first conductive portions and the second conductive portion, wherein, the third fiber layer is configured of a plurality of connecting yarns that is extended from one of the plurality of first conductive portions and the second conductive portion to another thereof to connect the plurality of first conductive portions and the second conductive portion, characterized in that: the plurality of connecting yarns further electrically connects the plurality of first conductive portions and the second conductive portion with a predetermined electric resistivity, respectively, and, when the first fiber layer or the second fiber layer is deformed by pressure application, a connecting yarn near the pressure application among the plurality of connecting yarns deforms due to the first or second fiber layer deformation and shortens a length of a conducting path (L, L') formed by the connecting yarn between the plurality of first conductive portions and the second conductive portion to reduce electric resistance between the plurality of first conductive portions and the second conductive portion. the plurality of connecting yarns further electrically connects the plurality of first conductive portions and the second conductive portion with a predetermined electric resistivity, respectively, and, when the first fiber layer or the second fiber layer is deformed by pressure application, a connecting yarn near the pressure application among the plurality of connecting yarns deforms due to the first or second fiber layer deformation and shortens a length of a conducting path (L, L') formed by the connecting yarn between the plurality of first conductive portions and the second conductive portion to reduce electric resistance between the plurality of first conductive portions and the second conductive portion.