伊古诺拉海上的圣十字大陆安特・依苏拉。魔王撒旦为了建立魔物的乐土，率领亚多拉玛雷克、艾谢尔、路西菲尔、以及马纳果达这四位恶魔大元帅进攻人类世界。然而此时手持圣剑的勇者出现了。

离征服世界只差一步的魔王撒旦，却被勇者打败而被迫漂流到了异世界的日本东京一个名叫笹冢的地方。 对于这个魔王能在日本做的事情，“征服世界！”——当然那是不可能的。于是在车站附近开始了打工生活的魔王大人，为了赚取生活费过起了飞特族的生活。 就在那个时候，同时穿越了时空来到日本的勇者大人艾米莉娅，也以接线员的身份开始了同日本经济斗争的日子。

在六帖榻榻米大小的假想魔王城之中，魔王大人挥汗如雨辛勤劳动的平民故事就此展开。

Striking fear into the hearts of mortals, the Demon Lord Satan begins to conquer the land of Ente Isla with his vast demon armies. However, while embarking on this brutal quest to take over the continent, his efforts are foiled by the hero Emilia, forcing Satan to make his swift retreat through a dimensional portal only to land in the human world. Along with his loyal general Alsiel, the demon finds himself stranded in modern-day Tokyo and vows to return and complete his subjugation of Ente Isla—that is, if they can find a way back!

Powerless in a world without magic, Satan assumes the guise of a human and begins working at MgRonald's to make ends meet. He soon realizes that his goal of conquering Ente Isla is just not enough as he grows determined to climb the corporate ladder and become the ruler of Earth,

Whether it's part-time work or household chores this anime presents a hilarious view of the most mundane aspects of everyday life, all through the eyes of a hapless demon lord.

｢はたらく魔王さま！｣は、勇者に敗れ、異世界エンテ・イスラから現代日本の東京にやってきた魔王サタンが、日本経済の荒波にもまれながらフリーターとして働く庶民派ファンタジー。魔王を追って日本にやってきた勇者エミリアもまた、テレアポとして生計を立てている。魔王と勇者でありながら、額に汗して働く二人が東京で再会することになり――？