The Diet on Friday revised the labor contract law to improve employers' treatment of contract workers hired for fixed durations and to ban their unreasonable dismissal.
The revised law gives the nation's estimated 12 million part-time or contract workers the option of becoming permanent staff after five years' employment at the same workplace.
The amendment also prohibits employers from refusing to renew such contracts when it is deemed reasonable for workers to expect to be retained. The revised law further outlaws "unreasonable" differences in the working conditions of contract and permanent employees.
A separate act, the Labor Standards Law, limits the term of a single contract to three years in principle, but employers often renew them repeatedly in practice.