A casing of an endoscopic manipulating head assembly is largely constituted by and dividable into a main cover section adapted to support an operating means of an angulation control mechanism and a grip cover section provided between the main cover section and an insertion tube of the endoscope. Both of the main cover section and the grip cover section are formed of a synthetic resin material. A support plate of a rigid metal is provided internally of the manipulating head assembly to support the angulation control mechanism. A plural number of passage-forming tubular structural members are successively connected within the grip cover section for passing internal components to and from the insertion tube of the endoscope. The support plate is connected to one of the tubular structural members which is located at the proximal end of the grip cover section. A first anti-twist lock portion is formed between the support plate and joined end portions of the main and grip cover sections, while a second anti-twist lock portion is formed between the grip cover section and joined end portions of the tubular structural members.