A porous film, being a separator of an electrochemical device, said porous film comprising: (a) a porous substrate having pores; and (b) a coating layer formed on at least one region selected from the group consisting of a surface of the substrate and a part of the pores present in the substrate, wherein the coating layer comprises styrene-butadiene rubber; characterized in that the porous substrate having pores is selected from the group consisting of: (i) an organic/inorganic composite porous film, which comprises a porous film having pores, coated with a coating layer comprising a mixture of inorganic particles with a binder polymer, on a surface of the porous film and/or on a part of the pores present in the porous film; and (ii) a freestanding type of organic/inorganic composite porous film comprising inorganic particles and a binder polymer coating layer partially or totally formed on the surface of the inorganic particles; said organic/inorganic composite porous films (i) and (ii) comprising the inorganic particles linked and fixed among themselves by the binder polymer, and have a pore structure formed by interstitial volumes of the inorganic particles; characterized in that: - the styrene-butadiene rubber has a glass transition temperature (Tg) of 25°C or less, and - the styrene-butadiene rubber contains a hydrophilic functional group. (a) a porous substrate having pores; and (b) a coating layer formed on at least one region selected from the group consisting of a surface of the substrate and a part of the pores present in the substrate, wherein the coating layer comprises styrene-butadiene rubber; characterized in that the porous substrate having pores is selected from the group consisting of: (i) an organic/inorganic composite porous film, which comprises a porous film having pores, coated with a coating layer comprising a mixture of inorganic particles with a binder polymer, on a surface of the porous film and/or on a part of the pores present in the porous film; and (ii) a freestanding type of organic/inorganic composite porous film comprising inorganic particles and a binder polymer coating layer partially or totally formed on the surface of the inorganic particles; said organic/inorganic composite porous films (i) and (ii) comprising the inorganic particles linked and fixed among themselves by the binder polymer, and have a pore structure formed by interstitial volumes of the inorganic particles; characterized in that: - the styrene-butadiene rubber has a glass transition temperature (Tg) of 25°C or less, and - the styrene-butadiene rubber contains a hydrophilic functional group. (i) an organic/inorganic composite porous film, which comprises a porous film having pores, coated with a coating layer comprising a mixture of inorganic particles with a binder polymer, on a surface of the porous film and/or on a part of the pores present in the porous film; and (ii) a freestanding type of organic/inorganic composite porous film comprising inorganic particles and a binder polymer coating layer partially or totally formed on the surface of the inorganic particles; - the styrene-butadiene rubber has a glass transition temperature (Tg) of 25°C or less, and - the styrene-butadiene rubber contains a hydrophilic functional group.