A transmission lubricating assembly for a helicopter, the transmission lubricating assembly comprising: a transmission including a speed change structure that is configured to be able to change the speed of rotation produced by rotational power input from a prime mover and output the resulting rotational power and a housing accommodating the speed change structure; and a lubricator (3, 13, 23) that lubricates the speed change structure, wherein the lubricator (3, 13, 23) includes a collector that collects a mist of a lubricating oil in an internal space of the housing and a dropper (31, 131) that is disposed below the collector and that applies droplets of the lubricating oil to the speed change structure, the droplets resulting from the collected mist being gathered under its own weight, characterised in that the lubricator (3, 13, 23) further includes a shaft structure extending in a horizontal direction and a tubular structure (14, 114) disposed to enclose an outer peripheral surface of the shaft structure, with a gap defined between an inner peripheral surface of the tubular structure (14, 114) and the outer peripheral surface of the shaft structure, one axial end of the tubular structure (14, 114) is located below the other axial end of the tubular structure (14, 114), the collector includes the outer peripheral surface of the shaft structure, an end surface of the shaft structure, and the inner peripheral surface of the tubular structure (14, 114), the end surface of the shaft structure being located towards the one axial end of the tubular structure (14, 114), the droplets of the lubricating oil are retained in the gap, and the dropper (31, 131) includes a lowermost point of a region of the shaft structure and a lowermost point of a region of the tubular structure (14, 114), the regions facing each other across the gap. a transmission including a speed change structure that is configured to be able to change the speed of rotation produced by rotational power input from a prime mover and output the resulting rotational power and a housing accommodating the speed change structure; and a lubricator (3, 13, 23) that lubricates the speed change structure, wherein the lubricator (3, 13, 23) includes a collector that collects a mist of a lubricating oil in an internal space of the housing and a dropper (31, 131) that is disposed below the collector and that applies droplets of the lubricating oil to the speed change structure, the droplets resulting from the collected mist being gathered under its own weight, characterised in that the lubricator (3, 13, 23) further includes a shaft structure extending in a horizontal direction and a tubular structure (14, 114) disposed to enclose an outer peripheral surface of the shaft structure, with a gap defined between an inner peripheral surface of the tubular structure (14, 114) and the outer peripheral surface of the shaft structure, one axial end of the tubular structure (14, 114) is located below the other axial end of the tubular structure (14, 114), the collector includes the outer peripheral surface of the shaft structure, an end surface of the shaft structure, and the inner peripheral surface of the tubular structure (14, 114), the end surface of the shaft structure being located towards the one axial end of the tubular structure (14, 114), the droplets of the lubricating oil are retained in the gap, and the dropper (31, 131) includes a lowermost point of a region of the shaft structure and a lowermost point of a region of the tubular structure (14, 114), the regions facing each other across the gap.