It was not unusual to see actresses acting male roles in the 17th century Spanish plays. Why did those playwrights have actresses act male roles despite of the difficulty imposed on them? In other words, what was the specific function of the male roles acted by women? There are two ways to think about its purposes or functions: on one hand, as a social message that the playwright tries to convey to the public, and on the other, a purely dramatic element that is intended to create an erotic visual effect to the audience. As well known, the age of Felipe III around 1600 to 1625, when 'Comedia Nueva' was in its heyday led by Lope and his followers who formed ‘Teatro nacional’, was one of the darkest moment in the Spanish society. The glory of the past imperialism was diminishing, and the poverty was everywhere in the nation, and even the outbreak of the plague stuck the whole nation so severely that the social instability reached an extreme. Thus the public distrust of the past values in Renaissance was prevalent, which rendered an ideological notion of the abrogation and the reformation of the past. This social aspiration of the change was reflected variously in Lope's pieces of comedies, and I argue that the women in male roles can also be examined in this context. In short, people's aspiration for the social change and the new values was reflected on the scenes that women act male roles with even more dramatic actions, and eliminate the absurdity of the past values. Also, the actresses in men's clothing created distinctively erotic effects for the time. It was because the actresses had to wear pants instead of skirts, which showed the shape of the women's legs to the audience. It was understandable why it had such an erotic effect considering the fact that people at that time could not even imagine any women wearing pants which exposed the shape of their legs. Hence those women in men's clothing gave a shockingly erotic fun to the Spanish people, who had no particular amusements other than going to the theaters. Thus it is not surprising that Lope, who concerned the popular trends more than anything, created many male roles acted by women in ‘Comedia Nueva’ of the age.