The present invention provides anti-aPC antibodies that suppress the inactivation of activated protein C (aPC), and uses thereof. The present inventors screened anti-aPC antibodies, and succeeded in isolating anti-aPC antibodies comprising the activity of suppressing aPC inactivation in blood. The antibodies of the present invention can be used to maintain aPC activity by suppressing aPC inactivation, and can thus be used to sustain aPC bioactivities, such as the activity of suppressing activation of the blood coagulation system, and anti-inflammatory activity. In addition, the present invention provides uses of the antibodies of the present invention in aPC therapy for diseases such as thrombosis and sepsis. The therapeutic effect of aPC can be prolonged in treatment that uses aPC administration by allowing an antibody of the present invention to bind with aPC. The antibodies of the present invention can be used in the treatment and prevention of diseases such as thrombosis and sepsis.