An apparatus for detecting an attachment of one component to another component comprising: a detection head having a pressing face for pressing a face of the one component, for detecting presence or absence of the one component or whether or not the one component is attached, the detection head including a movable element having a distal end portion capable of being brought into contact with a predetermined portion of the another component, a guide passage for guiding the movable element so as to be capable of reciprocal motion in an attachment direction of the one component, a fluid passage for passing a fluid when the distal end portion is brought into contact with the predetermined portion of the another component and pushed and the movable element is moved to a predetermined position, and a detection portion for detecting a pressure or a flow rate of the fluid flowing through the fluid passage, and a driving mechanism for driving the detection head in the attachment direction of the one component, characterized in that the fluid passage is formed so as to cross and communicate with the guide passage, the movable element has a communication path communicating with the fluid passage so as to allow a flow of the fluid when moved to the predetermined position, a diameter-reduced movable portion defining the distal end portion, and a diameter-enlarged movable portion having a diameter larger than that of the diameter-reduced movable portion and defining the communication path, the guide passage has a diameter-reduced guide passage for containing the diameter-reduced movable portion with a predetermined gap space, a diameter-enlarged guide passage (71c") slidably containing and guiding the diameter-enlarged movable portion and crossing and communicating with the fluid passage, and a stepped portion (71c"') formed at a boundary between the diameter-reduced guide passage and the diameter-enlarged guide passage (71c"), and the detection head includes a rear-end side auxiliary passage formed so as to pass the fluid outward from a side face close to a rear end side of the diameter-enlarged guide passage (71c") with respect to the fluid passage. a detection head having a pressing face for pressing a face of the one component, for detecting presence or absence of the one component or whether or not the one component is attached, the detection head including a movable element having a distal end portion capable of being brought into contact with a predetermined portion of the another component, a guide passage for guiding the movable element so as to be capable of reciprocal motion in an attachment direction of the one component, a fluid passage for passing a fluid when the distal end portion is brought into contact with the predetermined portion of the another component and pushed and the movable element is moved to a predetermined position, and a detection portion for detecting a pressure or a flow rate of the fluid flowing through the fluid passage, and a driving mechanism for driving the detection head in the attachment direction of the one component, characterized in that the fluid passage is formed so as to cross and communicate with the guide passage, the movable element has a communication path communicating with the fluid passage so as to allow a flow of the fluid when moved to the predetermined position, a diameter-reduced movable portion defining the distal end portion, and a diameter-enlarged movable portion having a diameter larger than that of the diameter-reduced movable portion and defining the communication path, the guide passage has a diameter-reduced guide passage for containing the diameter-reduced movable portion with a predetermined gap space, a diameter-enlarged guide passage (71c") slidably containing and guiding the diameter-enlarged movable portion and crossing and communicating with the fluid passage, and a stepped portion (71c"') formed at a boundary between the diameter-reduced guide passage and the diameter-enlarged guide passage (71c"), and the detection head includes a rear-end side auxiliary passage formed so as to pass the fluid outward from a side face close to a rear end side of the diameter-enlarged guide passage (71c") with respect to the fluid passage.