A connector for mounting a module of a wearable device on a garment to establish electrical connection therebetween, the connector comprising: a garment-side connector portion to be attached to the garment; and a module-side connector portion to be fitted to the garment-side connector portion, wherein the garment-side connector portion includes a garment-side connector body having a first fitting surface and a lateral wall surrounding the first fitting surface, and one or more first contacts disposed on the first fitting surface of the garment-side connector body, wherein the module-side connector portion includes a module-side connector body having a second fitting surface that, when the module-side connector portion is fitted with the garment-side connector portion, faces the first fitting surface and also having a lateral surface surrounding the second fitting surface, and one or more second contacts disposed in the second fitting surface of the module-side connector body, wherein a first waterproof member that is elastically deformable is disposed on one of the lateral wall of the garment-side connector body and the lateral surface of the module-side connector body so as to surround the first fitting surface or the second fitting surface, and wherein, when the module-side connector portion is fitted with the garment-side connector portion, the one or more first contacts and the one or more second contacts are electrically connected to each other, and the first waterproof member is elastically compressed between the lateral wall of the garment-side connector body and the lateral surface of the module-side connector body, whereby water is prevented from entering the first fitting surface and the second fitting surface, characterised in a locking portion disposed on the first fitting surface of the garment-side connector body, and a portion to be locked disposed on the second fitting surface of the module-side connector body, wherein the locking portion locks a position of the portion to be locked only when the module-side connector body is fitted with the garment-side connector body in a predetermined orientation. a garment-side connector portion to be attached to the garment; and a module-side connector portion to be fitted to the garment-side connector portion, wherein the garment-side connector portion includes a garment-side connector body having a first fitting surface and a lateral wall surrounding the first fitting surface, and one or more first contacts disposed on the first fitting surface of the garment-side connector body, wherein the module-side connector portion includes a module-side connector body having a second fitting surface that, when the module-side connector portion is fitted with the garment-side connector portion, faces the first fitting surface and also having a lateral surface surrounding the second fitting surface, and one or more second contacts disposed in the second fitting surface of the module-side connector body, wherein a first waterproof member that is elastically deformable is disposed on one of the lateral wall of the garment-side connector body and the lateral surface of the module-side connector body so as to surround the first fitting surface or the second fitting surface, and wherein, when the module-side connector portion is fitted with the garment-side connector portion, the one or more first contacts and the one or more second contacts are electrically connected to each other, and the first waterproof member is elastically compressed between the lateral wall of the garment-side connector body and the lateral surface of the module-side connector body, whereby water is prevented from entering the first fitting surface and the second fitting surface, characterised in a locking portion disposed on the first fitting surface of the garment-side connector body, and a portion to be locked disposed on the second fitting surface of the module-side connector body, wherein the locking portion locks a position of the portion to be locked only when the module-side connector body is fitted with the garment-side connector body in a predetermined orientation.