A water absorbing resin having a siloxane skeleton, being a copolymer comprising: a structural unit derived from a polymerizable vinyl monomer (A) shown by the following general formula , wherein, R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms; R 2 represents a hydrocarbon group having 1 to 6 carbon atoms or a group shown by the following general formula ; with the polymerizable vinyl monomer (A) optionally being a combination of the polymerizable vinyl monomers that differ in R 2 ; —(CH 2 ) a —(OC 2 H 4 ) b —(OC 3 H 6 ) c ―OR 3 wherein, "a" is an integer of 1 to 4, 0 ≤ b ≤ 30, 0 ≤ c ≤ 30, and 0 < b+c ≤ 40; R 3 represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms; a structural unit derived from a polymerizable vinyl monomer (B) shown by the following general formula , wherein, R 1 is as described above; X represents a hydrogen atom, an alkaline metal ion, an ammonium ion, or an organic ammonium ion; with the polymerizable vinyl monomer (B) optionally being a combination of the polymerizable vinyl monomers that differ in X; a structural unit derived from an organopolysiloxane (C) having polymerizable groups at the both terminals thereof shown by the following general formula , wherein, "k" is an integer of 1 to 4; R 1 is as described above; R 4 represents a hydrocarbon group having 1 to 8 carbon atoms; R 5 represents R 4 or a group shown by the general formula ; and "m" and "n" are integers of 0 ≤ m ≤ 100 and 0 ≤ n ≤ 20 satisfying 0 ≤ m+n ≤ 100, wherein, the polymerizable vinyl monomer (A) and/or the organopolysiloxane (C) comprise the group shown by the general formula . a structural unit derived from a polymerizable vinyl monomer (A) shown by the following general formula , wherein, R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms; R 2 represents a hydrocarbon group having 1 to 6 carbon atoms or a group shown by the following general formula ; with the polymerizable vinyl monomer (A) optionally being a combination of the polymerizable vinyl monomers that differ in R 2 ; —(CH 2 ) a —(OC 2 H 4 ) b —(OC 3 H 6 ) c ―OR 3 wherein, "a" is an integer of 1 to 4, 0 ≤ b ≤ 30, 0 ≤ c ≤ 30, and 0 < b+c ≤ 40; R 3 represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms; a structural unit derived from a polymerizable vinyl monomer (B) shown by the following general formula , wherein, R 1 is as described above; X represents a hydrogen atom, an alkaline metal ion, an ammonium ion, or an organic ammonium ion; with the polymerizable vinyl monomer (B) optionally being a combination of the polymerizable vinyl monomers that differ in X; a structural unit derived from an organopolysiloxane (C) having polymerizable groups at the both terminals thereof shown by the following general formula , wherein, "k" is an integer of 1 to 4; R 1 is as described above; R 4 represents a hydrocarbon group having 1 to 8 carbon atoms; R 5 represents R 4 or a group shown by the general formula ; and "m" and "n" are integers of 0 ≤ m ≤ 100 and 0 ≤ n ≤ 20 satisfying 0 ≤ m+n ≤ 100, wherein, the polymerizable vinyl monomer (A) and/or the organopolysiloxane (C) comprise the group shown by the general formula . <EOS>