An energy conversion device using change of contact surface contacting liquid, comprising: a) a first electrode substrate and a second electrode substrate which are spaced apart and facing each other; b1) the first electrode substrate or the second electrode substrate having an energy conversion layer (230, 240) stacked or deposited thereon, or b2) both the first electrode substrate and the second electrode substrate having a respective energy conversion layer (230, 240) stacked or deposited thereon, c) an ionic liquid or water which, in case b1), is in contact with the energy conversion layer (230, 240) and the electrode substrate on which the energy conversion layer (230, 240) is not stacked or deposited, and which, in case b2), is in contact with both respective energy conversion layers (230, 240); d) the respective energy conversion layer (230, 240), which is stacked or deposited on at least one of the first electrode substrate and the second electrode substrate, generating electrical energy in accordance with a change of an overlapping area of the contact surface between the ionic liquid or water and the energy conversion layer (230, 240) when the ionic liquid or water is moving in case b1) between the electrode substrate (210 or 220) and the energy conversion layer (230, 240), or in case b2) between the energy conversion layers (230, 240), e) wherein the energy conversion layer (230, 240) includes at least one of an inorganic material layer, an organic material layer or a layer comprising a mixture of organic and inorganic materials and wherein the inorganic material layer and/or the organic material layer is formed as a micro structure having shapes such as a convex-concave shape, a sharply protruded shape, a semi sphere shape, or a spherical pit shape for enlarging the contact surface contacting the ionic liquid or water. a) a first electrode substrate and a second electrode substrate which are spaced apart and facing each other; b1) the first electrode substrate or the second electrode substrate having an energy conversion layer (230, 240) stacked or deposited thereon, or b2) both the first electrode substrate and the second electrode substrate having a respective energy conversion layer (230, 240) stacked or deposited thereon, c) an ionic liquid or water which, in case b1), is in contact with the energy conversion layer (230, 240) and the electrode substrate on which the energy conversion layer (230, 240) is not stacked or deposited, and which, in case b2), is in contact with both respective energy conversion layers (230, 240); d) the respective energy conversion layer (230, 240), which is stacked or deposited on at least one of the first electrode substrate and the second electrode substrate, generating electrical energy in accordance with a change of an overlapping area of the contact surface between the ionic liquid or water and the energy conversion layer (230, 240) when the ionic liquid or water is moving in case b1) between the electrode substrate (210 or 220) and the energy conversion layer (230, 240), or in case b2) between the energy conversion layers (230, 240), e) wherein the energy conversion layer (230, 240) includes at least one of an inorganic material layer, an organic material layer or a layer comprising a mixture of organic and inorganic materials and wherein the inorganic material layer and/or the organic material layer is formed as a micro structure having shapes such as a convex-concave shape, a sharply protruded shape, a semi sphere shape, or a spherical pit shape for enlarging the contact surface contacting the ionic liquid or water.