To provide a polyelectrolyte which is superior in heat property, physical property and ion conductivity, and is close to practical use level, and to provide especially a full solid polyelectrolyte and a composite to manufacture it.

The composite for the solid polyelectrolyte contains the repeated unit indicated in formula (I) and in the formula (II), where R6and R8independently indicate a hydrogen atom and C1 to 10 hydrocarbon radical respectively. R7indicates the hydrogen atom, etc., and R9contains a copolymer provided with a repeating unit expressed by an organic radical provided with at least one type of functional group selected from a group consisting of hydroxyl group, carboxyl group epoxy radical, acid anhydride group and amino group, crosslinking agent as well as electrolyte salt.

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