Intracerebral hemorrhage (ICH) is devastating neurodegenerative disease that results from the leakage of blood constituents into brain parenchyma. Our previous research showed that leukotriene B₄ (LTB₄), a lipid mediator, promotes neutrophil invasion after ICH onset and exacerbates ICH pathology. Here we focused on microglia as the source of LTB₄ production. First, we checked the expression profiles of LTB₄ and other arachidonic acid metabolites in ICH brain. Male C57BL/6J mice were received the injection of typeⅦ collagenase (0.025 U) into striatum. Lipidomics analysis based on LC-MS/MS revealed the LTB₄ increase at 12 h after ICH induction. Then, we examined the effect of microglia-secreted mediators in ICH. Differentiated human promyelocytic leukemia cells (dHL-60) were seeded on upper layer of cell culture inserts with 3.0 μm pore, and treated culture supernatant of BV-2 cells with 12 h thrombin (30 U/mL) treatment to bottom layer. Culture supernatant of thrombin-treated BV-2 cells promotes infiltration of dHL-60 cells into the bottom layer, but U75302, a LTB₄ receptor 1 (BLT1) antagonist, suppressed the infiltration. These results suggest that LTB₄ secreted by microglia promote neutrophils invasion in ICH.