To comprehend a sentence, retrieval processes of both grammatical and lexical-semantic information from memory are required. However, previous studies had mainly focused on the maintenance process. The current fMRI study investigated the existence of information retrieval process on grammatical and lexical-semantic processing by manipulating retrieval load but by controlling maintenance load. Two tasks have prepared; in the grammatical task participants read ungrammatical Japanese coordination construction sentences and judged in which conjunct incongruent item had appeared, and in the lexical task, the participants remembered six Japanese words and judged when the lastly displayed word appeared. The result showed significant brain activity in the superior part and inferior part of left middle frontal gyrus in the grammatical task and in the lexical task, respectively (p<.001, uncorrected). This indicates the existence of retrieval system independently from maintenance process. In addition, grammatical information retrieval is processed distinctly from lexical-semantic information retrieval.