Method for spatio-spectral characterisation of a polychromatic pulsed laser source, in a device comprising: - a polychromatic pulsed laser source emitting a beam comprising a plurality of laser pulses with a spectral width ΔΩ in a direction of propagation z; - focussing optics that focus the beam in a focal plane in zo; - an imaging system for imaging a first plane of the beam in z1 in the vicinity of the focal plane z 0 and a second plane of the beam in z1 + dz, the imaging system comprising at least one camera; - an amplitude division interferometer arranged between the focussing optics and the camera and having first and second arms (18a, 18b); the method comprising, for each one of the first and second planes of the beam, the following steps: - imaging (101, 101') the beam plane (Pz1, Pz2) using the imaging system; - creating (102, 102) first and second replicas (13a, 13b) of the beam using first and second arms (18a, 18b) of the amplitude division interferometer; - recombining (103, 103') the first and second replicas (13a, 13b) of the beam on the camera of the imaging system, so as to obtain an image (Im1, Im2) in two spatial dimensions having spatial interference patterns; - measuring (104, 104') this image according to a time τ between the first and second replicas, the time τ sweeping a time interval Δt with a step dt, in order to obtain a temporal interferogram at each spatial point of the image (Im1, Im2), the set of temporal interferograms forming a spatio-temporal interferogram; - calculating (105, 105') the 1D Fourier transform of each temporal interferogram or the 3D Fourier transform of the spatio-temporal interferogram, said Fourier transform comprising a central frequency peak and two frequency side peaks; - filtering (106, 106') said Fourier transform so as to conserve only one of the two frequency side peaks; the method then comprising, for each frequency of the polychromatic pulsed laser source, a step of reconstructing the frequency-resolved spatial phase profile using a first frequency-resolved spatial amplitude profile obtained for the first beam plane and a second frequency-resolved spatial amplitude profile obtained for the second beam plane. - a polychromatic pulsed laser source emitting a beam comprising a plurality of laser pulses with a spectral width ΔΩ in a direction of propagation z; - focussing optics that focus the beam in a focal plane in zo; - an imaging system for imaging a first plane of the beam in z1 in the vicinity of the focal plane z 0 and a second plane of the beam in z1 + dz, the imaging system comprising at least one camera; - an amplitude division interferometer arranged between the focussing optics and the camera and having first and second arms (18a, 18b); - imaging (101, 101') the beam plane (Pz1, Pz2) using the imaging system; - creating (102, 102) first and second replicas (13a, 13b) of the beam using first and second arms (18a, 18b) of the amplitude division interferometer; - recombining (103, 103') the first and second replicas (13a, 13b) of the beam on the camera of the imaging system, so as to obtain an image (Im1, Im2) in two spatial dimensions having spatial interference patterns; - measuring (104, 104') this image according to a time τ between the first and second replicas, the time τ sweeping a time interval Δt with a step dt, in order to obtain a temporal interferogram at each spatial point of the image (Im1, Im2), the set of temporal interferograms forming a spatio-temporal interferogram; - calculating (105, 105') the 1D Fourier transform of each temporal interferogram or the 3D Fourier transform of the spatio-temporal interferogram, said Fourier transform comprising a central frequency peak and two frequency side peaks; - filtering (106, 106') said Fourier transform so as to conserve only one of the two frequency side peaks;