A binder and a slurry suitable for use in the production of an electrode in a sulfide-based solid-state battery. The binder contains sulfide-based solid electrolyte particles, and is a polymer including a vinylidene fluoride unit and at least one copolymerization unit (A) selected from a monomer unit having a structure represented by formula (1) below and a monomer unit having a structure represented by formula (2) below: where Rf1 and Rf2 are each a linear or branched fluorinated alkyl or fluorinated alkoxy group with 1 to 12 carbon atoms, which optionally contains an oxygen atom between carbon-carbon atoms when the number of carbon atoms is 2 or more. The slurry contains sulfide-based solid electrolyte particles, the binder and a solvent. Also disclosed is an electrode including an electrode active material layer formed using the slurry and a lithium-ion secondary solid state battery including the electrode.