The appeal is dismissed.

The costs of appeal shall be borne by the Plaintiff, including those incurred by supplementary participation.

The grounds of appeal are examined.

1. As to the grounds of appeal Nos. 1 and 3

A. Article 81 subparag. 1 of the Trade Union and Labor Relations Adjustment Act (hereinafter “Trade Union Act”) provides that “the act of dismissal or disadvantage of a worker on the ground that the worker has joined or was willing to join a trade union, or intended to organize a trade union, or that the worker has committed any other lawful act for the business of a trade union,” as one type of unfair labor practices committed by the employer.

In order to establish an unfair labor practice as referred to in the above provision, an employer must make a "justifiable act for the business of a trade union" and make a discriminatory act that gives disadvantages to workers, such as dismissal, on the ground of such act. The assertion of such fact and burden of proof are on the part of claiming that the act is an unfair labor practice.

On the other hand, if an employer at a place of business, whose level of personnel management and bonus payment for workers are subject to the criteria for bonus, has given disadvantage in paying bonus less than that of another trade union members or non-members on the ground that the employer is a member of a specific trade union, such employer’s act may also constitute unfair labor practices.

In such a case, whether an employer’s act constitutes unfair labor practice should be determined by comparing a group of union members of a specific trade union and a group of union members or non-members of a different trade union as a whole, and whether there was a statistical significant gap between both groups in personnel management and personnel management, whether there was objective circumstance to deem such gap between personnel management and personnel management was attributable to the employer’s anti-cooperative intent seeking to disadvantage on the ground that it was a member of a specific trade union, and even if there was no such discrimination in personnel management and personnel management, the same level of bonus has been paid.