There is provided a binder for ceramic formation or a conductive paste, comprising polyvinyl acetal having a degree of acetalization of from 50 to 85 mol %, a content of vinyl ester monomer unit of from 0.1 to 20 mol %, and having a viscosity-average degree of polymerization of from 200 to 5000, wherein a peak-top molecular weight (A) as measured by a differential refractive index detector and a peak-top molecular weight (B) as measured by an absorptiometer (measurement wavelength: 280 nm) in gel permeation chromatographic measurement of the polyvinyl acetal heated at 230° C. for 3 hours satisfy a formula (1) (A−B)/A