Rules of the Air Article 60

Except when necessary for take off or landing, or except by permission from the CAA, a VFR flight shall not be flown:1. over the congested areas of cities, towns or settlements or over an open-air assembly of persons at a height less than 1000 ft above the highest obstacle within a radius of 2000 ft from the aircraft.2. elsewhere at a height less than 500 ft above the ground or water.
中文原文 飛航規則第60條
目視飛航最低實際高度,除為起降需要或經民航局准許外,規定如下:
一、飛越城鎮之居住稠密地區或露天集會廣場上空時,其高度至少應在距航空器二千呎半徑範圍內最高障礙物上一千呎。
二、飛航其他地方時,不得低於距地面或水面五百呎。

English translation for reference only; the Chinese text prevails. Not legal advice.