The present invention relates to a method for preparing 2-pyrrolidone using biomass, comprising: a step (a) of culturing a microorganism which contains glutamate decarboxylase as a whole-cell catalyst in a culture medium containing glutamic acid or glutamate so as to prepare 4-amino butyric acid; a step (b) of filtering the 4-amino butyric acid from the culture medium in order to obtain the 4-amino butyric acid; and a step (c) of converting the 4-amino butyric acid into 2-pyrrolidone. The present invention provides a series of processes for preparing 2-pyrrolidone from glutamic acid or glutamate using biomass. According to the present invention, 4-amino butyric acid is prepared using a microorganism as a whole cell, and preferably, 4-amino butyric acid which has not undergone a complicated refining process such as a crystallization process is directly used to prepare 2-pyrrolidone at a high yield rate in an economically advantageous manner. According to the present invention, 2-pyrrolidone may be mass-produced at a high yield rate and low production costs. The method of the present invention simplifies processes for preparing 2-pyrrolidone, and thus is suitable for mass production at an industrial scale.