Provided are a paste composition capable of achieving a BSF effect which is equivalent to or greater than a conventionally achieved BSF effect even when used in either case where a thin back surface electrode layer is formed on a thick silicon semiconductor substrate or case where a thin back surface electrode layer is formed on a thin silicon semiconductor substrate and, when used in a case where a thin back surface electrode layer is formed on a thin silicon semiconductor substrate, not only capable of achieving a BSF effect which is equivalent to or greater than a conventionally achieved BSF effect, but also capable of more suppressing deformation of the silicon semiconductor substrate after being fired, than in a case where the conventional paste composition is used in order to form a thin back surface electrode layer; and a solar cell element comprising an electrode formed by using the paste composition. The paste composition comprises aluminum powder as electrically conductive powder and the aluminum powder includes flaky aluminum particles. The solar cell element comprises a back surface electrode (8) formed by applying the above-mentioned paste composition onto a back surface of a p-type silicon semiconductor substrate (1) and thereafter, firing a resultant.