A particle measuring apparatus comprising: a flow cell configured to flow a specimen; a first light source configured to emit a light having a first wavelength; a second light source configured to emit a light having a second wavelength different from the first wavelength; an irradiation optical system configured to irradiate the flow cell with the light emitted from the first light source and the second light source; a first light receiving portion configured to receive scattered light obtained by irradiating a measurement particle passing through the flow cell with the light from the first light source; and a second light receiving portion configured to receive scattered light obtained by irradiating the measurement particle passing through the flow cell with the light from the second light source; wherein the irradiation optical system comprises: a dichroic mirror configured to transmit the light emitted from the first light source and reflect the light emitted from the second light source, and a light collecting lens configured to collect the light emitted from the first and second light sources (101, 103) and passed through the dichroic mirror at the flow cell; characterised in that the particle measuring apparatus further comprises a base attached with the first light source, the second light source and the irradiation optical system; in that the second light source is turnably attached to the base; in that the dichroic mirror is attached to the base so as to be turnable in a direction different from a turning direction of the second light source; and in that a light collecting position of the light emitted from the second light source is displaced in one of a first direction that is parallel to the flow path of the flow cell and a second direction that traverses the flow path when the second light source is turned with respect to the base, and the light collecting position of the light emitted from the second light source is displaced in the other of the first and second directions when the dichroic mirror is turned with respect to the base. a flow cell configured to flow a specimen; a first light source configured to emit a light having a first wavelength; a second light source configured to emit a light having a second wavelength different from the first wavelength; an irradiation optical system configured to irradiate the flow cell with the light emitted from the first light source and the second light source; a first light receiving portion configured to receive scattered light obtained by irradiating a measurement particle passing through the flow cell with the light from the first light source; and a second light receiving portion configured to receive scattered light obtained by irradiating the measurement particle passing through the flow cell with the light from the second light source; wherein the irradiation optical system comprises: a dichroic mirror configured to transmit the light emitted from the first light source and reflect the light emitted from the second light source, and a light collecting lens configured to collect the light emitted from the first and second light sources (101, 103) and passed through the dichroic mirror at the flow cell; characterised in that the particle measuring apparatus further comprises a base attached with the first light source, the second light source and the irradiation optical system; in that the second light source is turnably attached to the base; in that the dichroic mirror is attached to the base so as to be turnable in a direction different from a turning direction of the second light source; and in that a light collecting position of the light emitted from the second light source is displaced in one of a first direction that is parallel to the flow path of the flow cell and a second direction that traverses the flow path when the second light source is turned with respect to the base, and the light collecting position of the light emitted from the second light source is displaced in the other of the first and second directions when the dichroic mirror is turned with respect to the base. a dichroic mirror configured to transmit the light emitted from the first light source and reflect the light emitted from the second light source, and a light collecting lens configured to collect the light emitted from the first and second light sources (101, 103) and passed through the dichroic mirror at the flow cell; characterised in that the particle measuring apparatus further comprises a base attached with the first light source, the second light source and the irradiation optical system; in that the second light source is turnably attached to the base; in that the dichroic mirror is attached to the base so as to be turnable in a direction different from a turning direction of the second light source; and in that a light collecting position of the light emitted from the second light source is displaced in one of a first direction that is parallel to the flow path of the flow cell and a second direction that traverses the flow path when the second light source is turned with respect to the base, and the light collecting position of the light emitted from the second light source is displaced in the other of the first and second directions when the dichroic mirror is turned with respect to the base.