An electromagnetic wave sensor 1 has electromagnetic wave absorbers disposed side by side in first and second directions, temperature detection portions held by the respective electromagnetic wave absorbers and sets of two arm portions connected to each electromagnetic wave absorber at two connection portions. In a plan view, the arm portions have two first extending portions extending from the connection portions in directions of which components in the second direction are opposite to each other, and two second extending portions extending from the first extending portions in directions of which components in the first direction are opposite to each other. Four sides of a rectangle circumscribing each of the electromagnetic wave absorbers with a smallest area are inclined with respect to the first direction in directions in which each electromagnetic wave absorber is away from the second extending portions with the connection portions as fulcrums.