An electronic circuit component mounting system comprising: a component supplying device (14, 16) that is configured to supply an electronic circuit component; a target member holding device that is configured to hold a mounting target member to which the electronic circuit component is to be mounted; a mounting device that includes a component holding tool which is configured to hold the electronic circuit component and a lifting and lowering device (58, 120, 122) which is configured to lift and lower the component holding tool, receive the electronic circuit component from the component supplying device (14, 16) using the component holding tool, and mount the electronic circuit component on the mounting target member held by the target member holding device; and a damage detecting device that is configured to detect that the electronic circuit component is damaged in at least one of when the component holding tool contacts the electronic circuit component by the component holding tool being lowered by the lifting and lowering device (58, 120, 122), and when the electronic circuit component held by the component holding tool contacts the mounting target member by the component holding tool being lowered by the lifting and lowering device (58, 120, 122); wherein the damage detection device includes a reaction force detecting section that is configured to detect a reaction force against the component holding tool in at least one of when the component holding tool contacts the electronic circuit component, and when the electronic circuit component held by the component holding tool contacts the mounting target member; and a damage determining section that is configured to determine presence or absence of damage of the electronic circuit component based on a changed state of the reaction force detected by the reaction force detecting section, wherein the damage determining section includes a reaction-force-change-state-dependent determination section which is configured to determine that the electronic circuit component is damaged in a case in which a changed state of the reaction force detected by the reaction force detecting section is different from a set change state which is set in advance by a state equal to or more than a set state, characterized in that the reaction-force-change-state-dependent determination section includes a reaction-force-rapid-decrease-dependent determination section which is configured to determine that the electronic circuit component is damaged in a case in which the reaction force detected by the reaction force detecting section rapidly decreases by an amount equal to or more than a set amount during an increase of the reaction force. a component supplying device (14, 16) that is configured to supply an electronic circuit component; a target member holding device that is configured to hold a mounting target member to which the electronic circuit component is to be mounted; a mounting device that includes a component holding tool which is configured to hold the electronic circuit component and a lifting and lowering device (58, 120, 122) which is configured to lift and lower the component holding tool, receive the electronic circuit component from the component supplying device (14, 16) using the component holding tool, and mount the electronic circuit component on the mounting target member held by the target member holding device; and a damage detecting device that is configured to detect that the electronic circuit component is damaged in at least one of when the component holding tool contacts the electronic circuit component by the component holding tool being lowered by the lifting and lowering device (58, 120, 122), and when the electronic circuit component held by the component holding tool contacts the mounting target member by the component holding tool being lowered by the lifting and lowering device (58, 120, 122); wherein the damage detection device includes a reaction force detecting section that is configured to detect a reaction force against the component holding tool in at least one of when the component holding tool contacts the electronic circuit component, and when the electronic circuit component held by the component holding tool contacts the mounting target member; and a damage determining section that is configured to determine presence or absence of damage of the electronic circuit component based on a changed state of the reaction force detected by the reaction force detecting section, wherein the damage determining section includes a reaction-force-change-state-dependent determination section which is configured to determine that the electronic circuit component is damaged in a case in which a changed state of the reaction force detected by the reaction force detecting section is different from a set change state which is set in advance by a state equal to or more than a set state, characterized in that the reaction-force-change-state-dependent determination section includes a reaction-force-rapid-decrease-dependent determination section which is configured to determine that the electronic circuit component is damaged in a case in which the reaction force detected by the reaction force detecting section rapidly decreases by an amount equal to or more than a set amount during an increase of the reaction force.