A micro-object detection apparatus comprising: a first optical system that includes a first reflection region, a second reflection region, a detection region surrounded by a first reflection region and the second reflection region and a first light reception element, the first optical system being configured to direct scattered light scattered when irradiation light hits a particle passing through the detection region, to the first light reception element, by reflecting the scattered light by the first reflection region and the second reflection region, wherein the first reflection region has an ellipsoidal shape, and is configured to reflect the scattered light coming from the particle to direct the scattered light to the first light reception element, by utilizing two focal point positions of the ellipsoida shape, wherein the second reflection region is configured to reflect the scattered light coming from the particle to direct the scattered light to the first reflection region, such that the scattered light is reflected by the first reflection region to the first light reception element, and wherein the first light reception element is configured to detect the intensity of the scattered light, the micro-object detection apparatus further comprising a second optical system that is configured to receive the scattered light and to detect a property of the particle based on the received scattered light, wherein the scattered light is directed to the first light reception element by providing a first passage region in the second reflection region and is directed to the second optical system by providing a second passage region in the first reflection region, and the second passage region is located to face the first passage region, and wherein the second optical system is configured to receive the scattered light that directly passes through the second passage region in the first reflection region, without being reflected by the first reflection region. a first optical system that includes a first reflection region, a second reflection region, a detection region surrounded by a first reflection region and the second reflection region and a first light reception element, the first optical system being configured to direct scattered light scattered when irradiation light hits a particle passing through the detection region, to the first light reception element, by reflecting the scattered light by the first reflection region and the second reflection region, wherein the first reflection region has an ellipsoidal shape, and is configured to reflect the scattered light coming from the particle to direct the scattered light to the first light reception element, by utilizing two focal point positions of the ellipsoida shape, wherein the second reflection region is configured to reflect the scattered light coming from the particle to direct the scattered light to the first reflection region, such that the scattered light is reflected by the first reflection region to the first light reception element, and wherein the first light reception element is configured to detect the intensity of the scattered light, the micro-object detection apparatus further comprising a second optical system that is configured to receive the scattered light and to detect a property of the particle based on the received scattered light, wherein the scattered light is directed to the first light reception element by providing a first passage region in the second reflection region and is directed to the second optical system by providing a second passage region in the first reflection region, and the second passage region is located to face the first passage region, and a second optical system that is configured to receive the scattered light and to detect a property of the particle based on the received scattered light, wherein the scattered light is directed to the first light reception element by providing a first passage region in the second reflection region and is directed to the second optical system by providing a second passage region in the first reflection region, and the second passage region is located to face the first passage region, and wherein the second optical system is configured to receive the scattered light that directly passes through the second passage region in the first reflection region, without being reflected by the first reflection region.