A connector is provided with a housing 10, a front seal portion 36 to be arranged to face a front surface of the housing 10, and a front wall portion 41 to be arranged to face a front surface of the front seal portion 36. The housing 10 includes cavities 17, deflectable locking lances 19 projecting into the cavities 17, and space portions 20 located in a deflection direction of the locking lances 19. The front wall portion 41 includes detection pieces 44 projecting rearward, tip sides of the detection pieces 44 being arranged in the space portions 20. The front seal portion 36 includes detection-side seal holes 40 to be held in close contact with base end sides of the detection pieces 44. The base end sides of the detection pieces 44 have a circular cross-sectional shape corresponding to the detection-side seal holes 40.