A soundproof structure has two or more soundproof units. Each of the soundproof units has an outer shell having a cylindrical shape, has a hollow inner space inside the outer shell, and has a first opening portion opened to outside on a surface that is one end portion of the outer shell in an axis direction of the cylindrical shape. The two soundproof units adjacent to each other are disposed in the axis direction such that the first opening portions face each other. The first opening portions facing each other are spaced apart from each other in the axis direction. An average distance in the axis direction between the first opening portions facing each other is less than 20 mm. Accordingly, there are provided a soundproof structure and a soundproof system which can insulate sounds on the low frequency side with a simple configuration, are small and lightweight, and can easily change the frequency characteristics.