A catheter apparatus has a catheter that is inserted into a lumen of the human body, a branch portion which is connected to a base end portion of the catheter and is provided with an insertion hole to pass a guide wire used in inserting the catheter in the lumen of the human body, and a liquid introducing portion for introducing liquid such as a drug solution into the catheter through a tube connected to the branch portion, where at a front end of the catheter is disposed embolus trapping part for trapping an embolus inside the lumen of the human body.