A process for producing carnitinamide which is an intermediate for production of L-carnitine is provided, which can hydrate carnitine nitrile to form carnitinamide with high selectivity, whereby highly-purified carnitinamide excellent as a substrate for stereoselective hydrolysis by optical resolution or a microorganism is produced in high yield. The process comprises hydrating carnitine nitrile to form carnitinamide using a catalyst containing a manganese oxide, and thus carnitinamide substantially free from by-produced carnitine is produced in high yield, so that carnitinamide of extremely high purity can be obtained through simple and easy crystallization operation.