Abstract: The problem to be solved by the invention is to provide an ionomer having excellent transparency, maintaining a high elastic modulus at high temperatures, being less coloration, and having a reduced odor during molding processing. The means for solving the problem is an ionomer comprising 0.05 to 1.0 mol % of (meth)acrylic acid ester units, 4.5 to 9.0 mol % of carboxylic acid units, 0.65 to 3.0 mol % of carboxylic acid neutralized product units, and ethylene units, based on the total monomer units which constitute the resin, with the total content of the (meth)acrylic acid ester units, the carboxylic acid units, and the carboxylic acid neutralized product units being 7.0 to 10 mol %.