A device for being mounted on board of a vehicle, comprising: a casing configured to be provided in a front portion of a vehicle cabin and in a vicinity of a center in a vehicle width direction, the casing configured to be provided such that a direction substantially orthogonal to a first center line, which is a center line of a first surface, extends along the vehicle width direction; a speaker adjacently provided to the first surface, inside the casing; and a first microphone and a second microphone adjacently provided to the first surface, inside the casing, the speaker, the first microphone, and the second microphone being arranged not to overlap each other when viewed in a direction facing the first surface, the speaker being provided such that, when viewed in the direction facing the first surface, the first center line and a second center line, which is a center line extending in a thickness direction of the speaker, overlap each other, and the first microphone and the second microphone being arranged at line-symmetric positions, with the first center line being a center therebetween, wherein the second center line is substantially orthogonal to the first surface, characterised in that a width of the first surface along the first center line is larger than a width of the first surface in a direction orthogonal to the first center line, when viewed in the direction facing the first surface, an angle (θ1) formed between a first line, which connects a point of intersection of the first center line and the second center line with a center of the first microphone, and a second line of the speaker is substantially from 10 degrees to 20 degrees, the second line being a center line substantially parallel with the first center line. a casing configured to be provided in a front portion of a vehicle cabin and in a vicinity of a center in a vehicle width direction, the casing configured to be provided such that a direction substantially orthogonal to a first center line, which is a center line of a first surface, extends along the vehicle width direction; a speaker adjacently provided to the first surface, inside the casing; and a first microphone and a second microphone adjacently provided to the first surface, inside the casing, the speaker, the first microphone, and the second microphone being arranged not to overlap each other when viewed in a direction facing the first surface, the speaker being provided such that, when viewed in the direction facing the first surface, the first center line and a second center line, which is a center line extending in a thickness direction of the speaker, overlap each other, and the first microphone and the second microphone being arranged at line-symmetric positions, with the first center line being a center therebetween, wherein the second center line is substantially orthogonal to the first surface, characterised in that a width of the first surface along the first center line is larger than a width of the first surface in a direction orthogonal to the first center line, when viewed in the direction facing the first surface, an angle (θ1) formed between a first line, which connects a point of intersection of the first center line and the second center line with a center of the first microphone, and a second line of the speaker is substantially from 10 degrees to 20 degrees, the second line being a center line substantially parallel with the first center line.