A layered titanic acid produced by subjecting a layered titanate represented by a general formula: A.sub.xM.sub.y.quadrature..sub.zTi.sub.2-(y+z)O.sub.4, wherein A and M represent metals having a valence of 1 to 3 and being different from each other, .quadrature. represents a defect to be occupied by titanium, x is a positive and real number satisfying 0