The present invention provides a cocrystal of (S)-3-( 1-(( l-acryloylpyrrolidin-3-yl)oxy)isoquinolin-3-yl)- l H- l ,2,4-triazol-5( 4H)-one and an organic acid capable of forming a cocrystal with the compound. Specific cocrystals prepared are cocrystals with gentisic acid,salicylic acid, maleic acid, malonic acid, malic acid, mandelic acid and citric acid.