Age discrimination refers to unreasonable differential treatment of a person or a group of people based on their age, and it has been mainly manifested in the field of employment. It occurs in various stages of employment and occupation, which is an act that infringes upon the equality right of workers. According to the manifestations of age discrimination, they can be divided into direct discrimination and indirect discrimination. Between them, the former can be observed or experienced directly. For example, employers use age as the sole criterion for hiring workers. However, indirect discrimination on the basis of age in employment and occupation is relatively difficult to distinguish. It means that the measures or decisions made by employers are apparently neutral and objective, but the results could adversely affect workers of a certain age. For instance, in the advertisement for hiring a porter, it is stated that employees must be proficient in using computers. Although it seems that there is no requirement for the age of the workers, most older workers do not have this skill. In order to fundamentally maintain the equal treatment in employment and occupation of workers, the legislative basis and judicial protection in related fields have become crucial. The first part of this essay will focus on the efforts of the EU in the anti-discrimination legislation. The following part will introduce the different approaches of justification of age discrimination under the relevant Directive of the EU. The third part will discuss the positive effect of EU law and the relevant precedent of the European Court of Justice on the protection of equal employment rights of workers. The last part of this essay will state that although the ability of Member States to justify age discrimination reveals certain deficiencies in relevant EU law and the European Court of Justice, it does not negate the protection of workers in employment and occupation at the EU level. Therefore, in order to ensure that workers are not discriminated against in the employment and occupation process, especially age discrimination, it requires not only the efforts of the EU legislature and the European Court of Justice but also the cooperation and supplementation of the legislature and the national court of Member States.